Monsters

Monsters refers to the many antagonistic creatures and entities Isaac can encounter throughout the game.

Most monsters (with few exceptions) damage Isaac by either touching him or shooting him with projectiles. Less frequently, monsters spawn additional, lesser monsters, spread creep, or attempt to affect Isaac's movement. Some monsters have scaled health depending on which floor they're encountered. Along with the more common variety of monsters, champion versions can be found lurking about; these monsters are often like their common counterparts, but have a color tint or size change, more health, and drop basic pickups on death. There are also champion versions of most bosses.

There are 336 naturally spawning monsters in total. 40 of them were added in Afterbirth, 21 were added in Afterbirth † (13 were added in Booster Packs) and 140 were added in Repentance. Almost all of these naturally spawning entities are featured in the Afterbirth+ Bestiary or Repentance Bestiary.

Monster List

Entity	ID	Description
Frowning Gaper	10.0	Walks towards Isaac, dealing contact damage. They start out with their eyes closed, but when they gain line of sight with Isaac, their eyes open and they permanently move faster. Usually turns into a Pacer or with a small chance a Gusher upon death.
Gaper	10.1	Walks towards Isaac, dealing contact damage. Usually turns into a Pacer or a Gusher upon death.
Flaming Gaper	10.2	Walks towards Isaac, dealing contact damage. Usually turns into a Pacer or Gusher upon death.
Rotten Gaper	10.3	Walks toward Isaac, dealing contact damage. Its behavior varies slightly depending on its facial expression.
Gurgle	87.0	Walks towards Isaac, dealing contact damage and periodically firing Ipecac shots at him; they are immune to this explosion, but other enemies are not. Can turn into a Splasher upon death.
Crackle	87.1	Walks toward Isaac, dealing contact damage and spitting fireballs that create lines of fire in the cardinal directions on impact.
Nulls	252.0	Walks towards Isaac, dealing contact damage. Upon getting near Isaac, it will open its eyes, though its speed doesn't change. Fades into and out of visibility.
Cyclopia	284.0	Walks towards Isaac, dealing contact damage and leaving behind a short-lasting trail of damaging Red Creep. Occasionally shoots a blood shot towards Isaac.
Blue Gaper	297.0	Walks towards Isaac, dealing contact damage.
Greed Gaper	299.0	Walks towards Isaac, dealing contact damage.
Wraith	807.0	Walks toward Isaac, dealing contact damage. They are invisible and can only be seen through the reflection they cast in the water, or the ripples they make as they walk.
Deep Gaper	811.0	Emerges from the floor once all previous enemies have been killed, then proceeds to chase Isaac. Deals contact damage.
Blurb	813.0	Walks slowly towards Isaac, dealing contact damage. After taking some damage or getting close to Isaac, it fires a chaotic burst of tears at him and chases him more quickly. Can turn into a Pacer or Gusher upon death.
Level 2 Gaper	850.0	Walks towards Isaac, dealing a full Heart of contact damage. Splits into a Level 2 Horf and Level 2 Gusher upon death.
Level 2 Horf	850.1	Slowly floats toward Isaac, spitting Small Maggots at him.
Level 2 Gusher	850.2	Runs aimlessly around the room, spitting up Small Maggots.
Twitchy	851.0	Alternates between walking towards and rapidly leaping at Isaac, dealing contact damage. Can leap to Isaac's current position, or where Isaac is heading, and can also leap away to dodge incoming fire.
Dead Isaac	912.20	Summoned by Mother at the bottom of the arena, they walk upward (ignoring Isaac completely), and deal contact damage. Releases a burst of blood shots upon being killed by Mother, while she launches their corpses towards Isaac.
Faceless	827.0	Wanders around the room, rarely firing a radial burst of six shots. Chases Isaac and fires shots more frequently after taking damage.
Tainted Faceless	827.1	Wanders around the room, rarely firing a radial burst of six shots. Chases Isaac and fires shots very frequently after taking damage.
Exorcist	832.0	Summons The Heretic before transforming into Fanatics.
Fanatic	832.1	Transformed into from Exorcists. Chases Isaac and occasionally fires two purple, rotating shots.
Candler	833.0	Flies around the room and propels itself by spawning flames.
Dump	876.0	Slides toward Isaac, leaving a trail of slippery brown creep. After taking enough damage, its head slides off and quickly bounces around the room and its body spews out brown shots until it empties.
Dump Head	876.1	Quickly slides toward Isaac, leaving a trail of slippery brown creep. Can spawn on its own or be created by a Dump after it takes enough damage.
Gusher	11.0	Walks aimlessly around the room, occasionally firing a short-ranged blood shot.
Pacer	11.1	Walks aimlessly around the room.
Splasher	238.0	Walks aimlessly around the room, firing Ipecac shots in random directions.
Black Globin's Body	280.0	Walks aimlessly around the room, occasionally spawning spiders.
Horf	12.0	Stationary enemy that fires a medium-ranged blood shot at Isaac when he gets in range of them.
Psychic Horf	248.0	Stationary enemy that fires a homing shot at Isaac when he gets in range of them.
Sub Horf	812.0	Stationary enemy that spins and fires shots while being moved around or knocked back.
Tainted Sub Horf	812.1	Will only shoot when hit. Takes heavy knockback and rotates when hit. Shoots a lot faster and has bigger projectiles than its normal variant.
Necro	828.0	Stationary enemy that summons unlimited-ranged bones to attack Isaac.
Fly	13.0	Hovers in place. Does not deal contact damage and is harmless, but can turn into Pooters if they stay around Poop.
Attack Fly	18.0	Red fly that follows Isaac and deals contact damage.
Moter	80.0	Follows Isaac, similar to Attack Flies. Deals contact damage. Splits into 2 Attack Flies upon death.
Eternal Fly	96.0	Invulnerable fly that circles Corny Poop and various monsters. Deals contact damage. Turns into a vulnerable Attack Fly after the object or monster it circles is destroyed.
Ring Fly	222.0	Gathers with any other Ring Flies in the room. These flies orbit around themselves while following Isaac. Deals contact damage.
Dart Fly	256.0	Flies towards Isaac and attempts to predict his movements. Deals contact damage.
Swarm	281.0	Follows Isaac in large, tightly-clustered groups and deals contact damage.
Hush Fly	296.0	Gathers with other Hush Flies to form certain patterns. If spawned by Hush, can chase Isaac or orbit Hush. Deals contact damage.
Willo	808.0	Flies in a circle around Isaac (in formation with other Willos if available), keeping an exact distance away from him. One Willo at a time will occasionally light up and fire a shot at Isaac.
Army Fly	868.0	Chases Isaac, moving along the cardinal directions. Forms a line with other Army Flies in the room. Deals contact damage.
Ultra Famine Fly	951.11	Charges at Isaac at a delay. Deals contact damage. Spawned by Ultra Famine.
Ultra Pestilence Fly	951.21	Flies in swarms around Ultra Pestilence, blocking shots and dealing contact damage.
Fly Bomb	819.0	Flies toward Isaac, circling around him as it does. Turn into a tiny Bomb upon death.
Eternal Fly Bomb	819.1	Orbits Boom Flies spawned by The Horny Boys. Once its Boom Fly has been killed, turns into a tiny Bomb.
Sucker	61.0	Flies slowly towards Isaac, exploding into 4 shots in the cardinal directions upon death.
Spit	61.1	Flies slowly towards Isaac, firing an Ipecac shot towards Isaac upon death.
Ink	61.3	Flies slowly towards Isaac. Fires four shots in the ordinal directions and leaves a puddle of slowing Black Creep upon death.
Soul Sucker	61.2	Flies slowly towards Isaac. Spawns a vortex that fires four Brimstone beams in the cardinal directions upon death.
Mama Fly	61.4	Flies more-or-less away from Isaac, occasionally plopping on the ground to plant a Pustule. Upon death, they spawn a group of Small Maggots.
Bulb	61.5	Flies in erratic, angled movements toward Isaac if his active item has charges; on contact, they drain up to 2 charges, but never deal contact damage. If he has no active item, or no charges, they wander around the room aimlessly.
Bloodfly	61.6	Spawned only after a Pustule bursts. Flies in erratic, angled movements toward Isaac. Fires four blood shots in the cardinal directions upon death.
Tainted Sucker	61.7	Flies slowly towards Isaac. Upon death, fires a radial burst of six blood shots that each also fires a radial burst of six blood shots.
Pooter	14.0	Slowly drifts toward Isaac, occasionally firing a single blood shot at him. Does not deal contact damage.
Super Pooter	14.1	Slowly drifts toward Isaac, occasionally firing two blood shots in a V-formation at him. Does not deal contact damage.
Tainted Pooter	14.2	Slowly drifts toward Isaac, occasionally firing four blood shots at him that split into two smaller ones when they hit a wall or obstacle.
Clotty	15.0	Randomly wanders around the room, firing 4 blood shots in the cardinal directions.
Clot	15.1	Randomly wanders around the room, firing 4 tar shots in the ordinal directions.
I.Blob	15.2	Randomly wanders around the room, firing 8 shots in all directions.
Grilled Clotty	15.3	Quickly and randomly wanders around the room, firing four flame shots in the cardinal directions at a slight angle.
Cloggy	872.0	Randomly wanders around the room, firing four curved brown shots in the cardinal directions. These shots alternate between rotating clockwise and counterclockwise with each shot.
Mulligan	16.0	Walks around the room, avoiding Isaac. Upon death, spawns several flies, which can be Flies, Attack Flies, and/or Pooters. Can self-detonate and launch four projectiles in the cardinal directions while still releasing flies.
Mulligoon	16.1	Walks around the room, avoiding Isaac. Upon death, spawns a Troll Bomb and fires four shots in the ordinal directions. Can self-detonate, spawn a Troll bomb, and launch eight projectiles in all directions.
Mulliboom	16.2	Chases Isaac and explodes upon death or upon touching Isaac. The explosion deals a half-heart of damage instead of the regular full heart.
Hive	22.0	Wanders around the room, avoiding Isaac and spawning Attack Flies if he gets close. Spawns a large number of flies on death, which can be Flies, Attack Flies, and/or Pooters.
Drowned Hive	22.1	Wanders around the room, avoiding Isaac and spawning Drowned Chargers if he gets close. Spawns 0-2 Drowned Chargers upon death.
Holy Mulligan	22.2	Wanders around the room, avoiding Isaac and spawning Angelic Baby (small) if he gets close. Spawns 1-2 Embryos upon death.
Tainted Mulligan	22.3	Wanders around the room, avoiding Isaac and spawning 6 Ring Flies if he gets close. Spawns a plethora of fly enemies upon death.
Nest	205.0	Wanders around the room, avoiding Isaac and spawning Spiders if he gets close. Spawns a Big Spider or Trite upon death.
Leper	310.0	Alternating between walking towards and running away from Isaac. Releases a Leper Flesh each time it takes enough damage. At low health, constantly chases Isaac and leaves behind damaging red creep. Spawns a Leper Flesh and Gusher upon death.
Leper Flesh	310.1	Floats slowly toward Isaac and fires a predictive projectile at him upon death.
Prey	817.0	Wanders around the room, avoiding Isaac and spawning Small Leeches if he gets close. Spawns 3 Small Leeches upon death.
Mullighoul	817.1	Wanders around the room, avoiding Isaac and spawning Willos if he gets close. Spawns 1-2 Willos upon death.
Bouncer	822.0	Wanders around the room, avoiding Isaac. If Isaac stays close to one for long enough, it inflates and starts chasing him, gaining a chance to deflect shots and causing it to explode into lingering blood shots on death.
Gas Dwarf	874.0	Chases Isaac, periodically coughing up gas clouds. On death, fires an explosive shot that can detonate gas clouds it hits.
Danny	820.0	Walks toward Isaac and spits chaotic bursts of rocks at him, some of which may be Rock Spiders.
Coal Boy	820.1	Walks toward Isaac and spits hot coals at him, some of which may be Coal Spiders.
Blaster	821.0	Slowly wanders around and occasionally shoots Fly Bombs at Isaac.
Maggot	21.0	Aimlessly moves around the room, dealing contact damage.
Charger	23.0	Slowly moves around the room, charging at Isaac when he gets in its line of sight.
My Shadow	23.0	Charges at enemies when in its line of sight, dealing contact damage. Will always spawn friendly via My Shadow.
Drowned Charger	23.1	Slowly moves around the room, charging at Isaac when he gets in its line of sight. Explodes into four blood shots in the ordinal directions upon death.
Dank Charger	23.2	Slowly moves around the room, launching itself at Isaac if he gets in its line of sight. Bounces off of walls and leaves a trail of slowing black creep while charging.
Carrion Princess	23.3	Slowly moves around the room, charging at Isaac when he lines up diagonally with it. Can only be damaged by hitting its tail.
Small Leech	810.0	Chases Isaac continuously, not stopping at walls. Able to swim over gaps.
Small Maggot	853.0	Slowly crawls toward Isaac, dealing contact damage.
Level 2 Charger	855.0	Slowly moves around the room, charging at Isaac when he gets in its line of sight. Can slowly change its trajectory while charging.
Elleech	855.1	Slowly moves around the room. After Isaac gets in its line of sight, continuously charges at him in the closest cardinal direction.
Blood Puppy	802.0	Quickly moves around the room, attacking and charging at other monsters and Isaac when they get in its line of sight.
Spitty	31.0	Slowly moves around the room, occasionally firing a single blood shot forward.
Tainted Spitty	31.1	Slowly moves around the room, firing chaotic bursts of blood shots in all directions and occasionally spitting a line of blood shots in the direction it's facing. Fires two rotating rings of blood shots upon death.
Conjoined Spitty	243.0	Slowly moves around the room, occasionally firing a blood shot from both ends of its body.
Globin	24.0	Chases Isaac, dealing a full heart of contact damage. Upon taking enough damage, it collapses into a pile of goo, which can be killed. Will regenerate after a short period of time if not killed quickly.
Gazing Globin	24.1	Quickly chases Isaac, dealing a full heart of contact damage. Upon taking enough damage, it collapses into a pile of goo, which will slide away from Isaac and can be killed. Will regenerate after a short period of time if not killed quickly.
Dank Globin	24.2	Chases Isaac, dealing a full heart of contact damage. Upon taking enough damage, it collapses into a pile of goo, spawns a Spider, and leaves a puddle of slowing Black Creep. Will regenerate after a short time if not killed quickly. Leaves another puddle of Black Creep upon death.
Cursed Globin	24.3	Chases Isaac, dealing a full heart of contact damage. Upon taking enough damage, it collapses into 1-2 piles of goo, each of which can be killed and regenerate after a short period of time if not killed quickly. These goo piles have less health the more times the Cursed Globin splits.
Black Globin	278.0	Chases Isaac, dealing a full heart of contact damage and launching Spiders towards Isaac whenever it takes damage. Spawns a Spider, a Black Globin's Head, and a Black Globin's Body upon death.
Clickety Clack	889.0	Walks towards Isaac and turn into a pile of bones when killed. Regenerates a few seconds after killed. Will only despawn if all Clickety Clacks in the room are killed.
Gasbag	856.0	Occasionally summons Army Flies to chase Isaac. Is surrounded by a ring of toxic gas that hurts Isaac if he stands in it for too long.
Cohort	857.0	Acts similarly to Monstro, hopping towards Isaac and can either spit a large projectile towards Isaac that bursts into 8 smaller projectiles or cough up a burst of arcing projectiles and a pile of Globin goo. Spawns 4 piles of Globin goo upon death.
Boom Fly	25.0	Flies across the room in straight diagonal lines, dealing contact damage. Explodes upon death.
Red Boom Fly	25.1	Flies across the room in straight diagonal lines, dealing contact damage. Creates a ring of 6 blood shots upon death.
Drowned Boom Fly	25.2	Flies across the room in straight diagonal lines, dealing contact damage. Upon death, explodes and fires four blood shots in the cardinal directions. Also has a chance to spawn a Drowned Charger upon death.
Dragon Fly	25.3	Flies across the room in straight diagonal lines, dealing contact damage. Upon death, creates four lines of fire in the cardinal directions; the fire nearly spans the length of an entire normal-sized room.
Dragon Fly X	25.3.1	Flies across the room in straight diagonal lines, dealing contact damage. Upon death, creates four lines of fire in the ordinal directions; the fire nearly spans the length of an entire normal-sized room.
Bone Fly	25.4	Flies across the room in straight diagonal lines, dealing contact damage. Fires bones at Isaac if he lines up with it in the cardinal directions. Fires a radial burst of 3 bones upon death.
Sick Boom Fly	25.5	Flies across the room in straight diagonal lines, dealing contact damage and trailing poisonous gas. Upon death, explodes into a gas cloud and fires a ring of 6 green shots.
Tainted Boom Fly	25.6	Flies across the room in straight diagonal lines, dealing contact damage. Upon death, it glows brightly, warning that it is about to explode; this explosion sends 4 lines of further explosions in the cardinal directions, which span the length of the room.
Maw	26.0	Slowly floats towards Isaac, firing a blood shot at him when he is in their range.
Red Maw	26.1	Floats quickly towards Isaac and releases 4 blood shots in the cardinal directions upon death.
Psychic Maw	26.2	Slowly floats towards Isaac, firing homing shots at him when he is in their range. Spawns with an Eternal Fly orbiting around it.
Host	27.0	Stationary enemy that is normally invulnerable. Raises its head up when Isaac gets close, revealing a fleshy stem that can be damaged. Upon raising its head, it will fire 3 blood shots in a spread and lower its head again.
Red Host	27.1	Stationary enemy that can be damaged even when its head is lowered. Fire 5 spread blood shots when it raises its head.
Hard Host	27.3	Stationary enemy that is normally invulnerable. Raises its head up when Isaac gets close, revealing a fleshy stem that can be damaged. Shortly after raising its head, it slams its head down and fires a rock wave towards Isaac.
Mobile Host	204.0	Acts like the Host, but follows Isaac and deals contact damage.
Flesh Mobile Host	247.0	Acts like the Red Host, but follows Isaac and deals contact damage.
Floast	859.0	Floats diagonally around the room and is normally invulnerable. When Isaac gets close, reveals a fleshy stem that can be damaged and fires 3 blood shots in an angle at him before hiding its stem again.
Mushroom	300.0	Stationary enemy that occasionally pops up and fires four shots in the cardinal or diagonal directions. Takes less damage while its head is down.
Hopper	29.0	Slowly hops around the room, doing contact damage. Can turn into a Flaming Hopper by jumping into Fire Places or other fires.
Eggy	29.2	Hops aimlessly around the room, spawning slowing white creep wherever it hops. Spawns a group of Swarm Spiders upon death.
Tainted Hopper	29.3	Jumps and twirls around the room, shooting 4 rings of projectiles that increase in size with each shot.
Leaper	34.0	Hops around the room, doing contact damage. Occasionally jumps high into the air, dropping down onto Isaac's position while firing 4 blood shots in the cardinal directions.
Sticky Leaper	34.1	Hops around the room, dealing contact damage. Occasionally jumps high into the air, dropping down onto Isaac's position while creating a chaotic burst of tar shots in all directions and a puddle of slowing black creep.
Flaming Hopper	54.0	Quickly hops around the room, doing contact damage. Covers a larger distance than the regular Hopper.
Trite	29.1	Quickly leaps towards Isaac and deals contact damage.
Ragling	246.0	Quickly leaps towards Isaac and deals contact damage. Randomly shoots two purple shots that orbit around it.
Rag Man's Ragling	246.1	Quickly leaps towards Isaac and deals contact damage. Randomly shoots two purple shots that orbit around it.
Blister	303.0	Slowly hops towards Isaac, occasionally spawning a Dark Ball. Spawns a Sack upon death.
Boil	30.0	Stationary enemy that decreases in size when hit, but regenerates to its full size until fully destroyed. Fires multiple short-ranged blood projectiles in random directions when fully swollen.
Gut	30.1	Stationary enemy that decreases in size when hit, but regenerates to its full size until fully destroyed. Fires Ipecac shots in random directions when fully swollen.
Sack	30.2	Stationary enemy that decreases in size when hit, but regenerates to its full size until fully destroyed. Occasionally spawns Spiders when fully swollen.
Blue Boil	298.0	Stationary enemy that decreases in size when hit, but regenerates to its full size until fully destroyed. Fires 1-3 blood shots towards Isaac when fully swollen.
Gush	309.0	Stationary, harmless enemy that continually creates slowing black creep.
Pustule	861.0	Slowly increases in size over time, spawning Small Maggots and damaging red creep depending on its size upon death. If it grows to full size, it transforms into a Bloodfly.
Walking Boil	88.0	Does not shrink or regenerate. Walks around aimlessly and fires multiple short-ranged blood projectiles in random directions.
Walking Gut	88.1	Does not shrink or regenerate. Walks around aimlessly and fires Ipecac shots in random directions.
Walking Sack	88.2	Does not shrink or regenerate. Walks around aimlessly and occasionally spawns Spiders.
Brain	32.0	Slowly crawls around the room, leaving a trail of red creep.
Black Globin's Head	279.0	Slides towards Isaac, leaving a trail of damaging red creep.
Festering Guts	831.20	Spawned by Gutted Fatties, Festering Guts randomly slide around the room and occasionally spawn a Charger.
Poison Mind	301.0	Slowly crawls/floats around the room diagonally, leaving a trail of damaging green creep. Explodes upon death.
Pon	840.0	Hops around the room, leaving damaging red creep wherever it lands. Upon death, its associated Brainless Knight dies with it.
Gyro	824.0	Rolls around like a wheel. Charges at Isaac when he is in line of sight, bouncing off of walls and obstacles as it does.
Grilled Gyro	824.1	Rolls around like a wheel. Charges at Isaac when he is in line of sight, bouncing off of walls and obstacles and creating fires behind itself as it does.
Mr. Maw	35.0	Walks towards Isaac and attacks by launching its head towards him. Turns into a Maw or Gusher upon death depending on the killed body segment. Occasionally separates at will.
Mr. Red Maw	35.2	Walks towards Isaac and attacks by launching its head towards him. Turns into a Red Maw or Gusher upon death depending on the killed body segment. Occasionally separates at will.
Swinger	216.0	Slowly moves towards Isaac as its head swings around its base. Upon death, spawns a Maw or a Globin depending on which part is killed.
Mr. Mine	311.0	Can only appear in pits. Attempts to launch itself at Isaac if he comes near. Occasionally burrows and pops up in another pit, and fires six shots in all directions upon death.
Baby	38.0	Slowly floats towards Isaac and fires a blood shot at him. Occasionally teleports and reappears elsewhere.
Angelic Baby	38.1	Slowly floats towards Isaac and fires three spread shots. Occasionally teleports and reappears elsewhere.
Angelic Baby (small)	38.1.1	Slowly floats towards Isaac and fires a blood shot at him. Occasionally teleports and reappears elsewhere. Can only be spawned by Holy Mulligans.
Wrinkly Baby	38.3	Dashes towards Isaac at high speed and fires three blood shots in his direction once stopped.
Imp	259.0	Slowly drifts towards Isaac, frequently firing 5 blood shots in quick succession towards him. Tries to avoid Isaac's shots and occasionally teleports and reappears elsewhere.
Unborn	860.0	Floats quickly towards Isaac, and occasionally teleports to another position near him.
Baby Begotten	883.0	Floats toward Isaac, avoiding his tears. After getting close, fires a short Brimstone laser in the closest cardinal direction and propels itself away from him.
Vis	39.0	Randomly wanders around the room. Pauses to charge and fire a Brimstone laser when Isaac gets in its line of sight.
Double Vis	39.1	Randomly wanders around the room. Pauses to charge and fire a Brimstone laser which fires from both sides when Isaac gets in its line of sight.
Chubber	39.2	Randomly wanders around the room. Pauses to fire a Charger that deals one heart of damage when Isaac gets in its line of sight. The Charger is invulnerable, blocks Isaac's tears, has limited range, and flies back to the Chubber.
Scarred Double Vis	39.3	Randomly wanders around the room. Pauses to charge and fire a Brimstone laser which fires from all four cardinal sides when Isaac gets in its line of sight.
Vis Versa	836.0	Randomly wanders around the room. Pauses to charge and fire a homing Brimstone laser when Isaac gets in its line of sight.
Evis	865.0	Randomly wanders around the room. Launches a string of guts when Isaac gets close to it, which it uses to pull Isaac toward itself.
Guts	40.0	Attaches itself to a wall or obstacle and rolls around it.
Scarred Guts	40.1	Attaches itself to a wall or obstacle and rolls around it, leaving a trail of damaging Red Creep.
Slog	40.2	Attaches itself to a wall or obstacle and rolls around it, charging at Isaac when he is in sight.
Cyst	862.0	Attaches itself to a wall or obstacle and rolls around it, regularly firing blood shots at Isaac.
Knight	41.0	Moves erratically around the room and charges towards Isaac when in line of sight. Can only be damaged from behind.
Selfless Knight	41.1	Moves erratically around the room and charges towards Isaac very quickly when in line of sight. Can only be damaged from behind.
Loose Knight	41.2	Moves erratically around the room, charges toward Isaac when in line of sight. When its health is depleted, it turns into a Brainless Knight and a Pon.
Brainless Knight	41.3	Alternates between running around the room along the cardinal directions and aimlessly walking in circles. Charges at Isaac when in line of sight. Dies when its corresponding Pon dies.
Black Knight	41.4	Moves erratically around the room, charges toward Isaac when in line of sight. Unleashes waves of fire in all cardinal directions upon charging into an obstacle. Shots that hit it from the front are deflected back at Isaac.
Floating Knight	254.0	Behaves like the Knight but slower, and can fly over all obstacles.
Bone Knight	283.0	Moves erratically around the room, charges toward Isaac when in line of sight, and leaves behind a short-lasting trail of damaging Red Creep. Can only be damaged from behind.
Whipper	834.0	Runs around the room, sprinting at Isaac when he gets in its line of sight and lashing at him when it gets close.
Snapper	834.1	Runs around the room, sprinting at Isaac when he gets in its line of sight and throwing out its whip when he gets in range.
Flagellant	834.2	Runs around the room. When Isaac gets in its line of sight, continuously chases him and lashes its whip, occasionally deflecting Isaac’s shots.
Dople	53.0	Mirrors Isaac's movements and fires blood shots at the same time as Isaac. Can be damaged by spikes.
Evil Twin	53.1	Mirrors Isaac's movements and fires three spread blood shots at the same time as Isaac. Can fly over obstacles.
Leech	55.0	Quickly charges towards Isaac when he gets in its line of sight.
Kamikaze Leech	55.1	Quickly charges towards Isaac when he gets in its line of sight. Explodes upon death.
Holy Leech	55.2	Quickly charges towards Isaac when he gets in its line of sight. Explodes upon death. Spawns with an Eternal Fly circling it, which instantly dies when the Holy Leech explodes.
Adult Leech	854.0	Wanders around the room, quickly charging at Isaac when he lines up horizontally with him and releasing a ring of blood shots upon colliding with a wall. After taking a certain amount of damage, burrows into the ground and reappears by falling above Isaac, releasing another ring of blood shots and only performing this behavior once.
Lump	56.0	Fires 3 spread blood shots at Isaac when he gets in its line of sight. Will burrow underground and reappear elsewhere after firing.
Tar Boy	307.0	Fires a short-ranged spray of shots that leave behind slowing Black Creep. Occasionally burrows underground and reappears under any pools of black creep in the room. If Isaac stands on the Creep, the Tar Boy can fire shots straight upwards out of the Creep underneath Isaac/ send out a tentacle underneath Isaac.
MemBrain	57.0	Slowly moves around the room, occasionally hopping and firing 8 large blood shots in all directions. Splits into 2 Brains upon death.
Mama Guts	57.1	Slowly moves around the room, occasionally hopping and firing 8 large blood shots in all directions. Splits into 2 Guts upon death.
Dead Meat	57.2	Slowly moves around the room, occasionally hopping and firing 8 large blood shots in all directions that bounce off the walls. Splits into 2 Cysts upon death.
Dinga	223.0	Slowly moves around the room, occasionally hopping to spawn Dips or fire 8 Brown shots in all directions. Splits 2 Squirts upon death.
Mega Clotty	282.0	Slowly moves around the room, occasionally hopping and either firing 6 blood shots in all directions, leaving a puddle of Red Creep, or spawning a Clotty or a collapsed Globin. Splits into two Clotties upon death.
Para-Bite	58.0	Moves towards Isaac, dealing contact damage. Can burrow underground and reappear elsewhere.
Scarred Para-Bite	58.1	Moves towards Isaac, dealing contact damage and firing a short-range blood shot at him. Can burrow underground and reappear elsewhere.
Fred	59.0	Hops out of the ground and burrows elsewhere, firing 4 blood shots in the cardinal directions. Occasionally fires red Ipecac shots at Isaac.
Eye	60.0	Slowly turns towards Isaac and fires a Technology laser at Isaac if he stands still or is too slow.
Bloodshot Eye	60.1	Slowly turns towards Isaac and fires a Brimstone beam at Isaac if he stands still or is too slow.
Holy Eye	60.2	Rapidly summons several beams of light around Isaac every few seconds.
Embryo	77.0	Aimlessly hops around the room, dealing contact damage.
Spider	85.0	Erratically moves around the room. If Isaac gets close to it, it chases him, trying to deal contact damage.
Big Spider	94.0	Erratically moves around the room. If Isaac gets close to it, it chases him, trying to deal contact damage. Spawns two Spiders upon death.
Strider	814.0	Erratically swims around the room. If it sees Isaac, it chases him, trying to deal contact damage.
Rock Spider	818.0	Slowly crawls around the room. If it sees Isaac, it crawls at him, trying to deal contact damage. Turns into a Spider upon death. Turns into a Coal Spider if it touches fire.
Tinted Rock Spider	818.1	Quickly crawls around the room. If it sees Isaac, it crawls at him, trying to deal contact damage. Turns into a Soul Heart upon death. Can only spawn by breaking tinted rocks on Mines or Ashpit.
Coal Spider	818.2	Quickly crawls around the room. If it sees Isaac, it crawls at him, trying to deal contact damage. Turns into a hot coal upon death that blocks shots and deals contact damage, but can be destroyed.
Swarm Spider	884.0	Very erratically hops toward Isaac in large groups, dealing contact damage.
Keeper	86.0	Hops around the room, firing 2 blood shots in a V formation at Isaac. Upon damaging Isaac, Isaac drops 2 coins on the ground but loses 3.
Buttlicker	89.0	Can start attached to other Buttlickers and erratically moves around the room, similar to Larry Jr..
Butt Slicker	878.0	Moves erratically around the room unless attached to another Butt Slicker. Grouped Butt Slickers drag themselves towards Isaac, and when an individual is killed they leave black creep, and shoot out black projectiles. The amount of projectiles released and the size of the pool of Black Creep is determined by the amount of Butt Slickers attached.
Hanger	90.0	Floats around the room, firing 3 spread blood shots at Isaac. Upon damaging Isaac, Isaac drops 2 coins on the ground but loses 3. Spawns with an Eternal Fly circling around it.
Swarmer	91.0	Slowly floats around the room, spawning several Attack Flies. Spawns Pooters upon taking damage. Spawns a Boom Fly upon death.
Mask + Heart	93.0	The Mask is invulnerable and moves around erratically, charging at Isaac when he lines up with it. The Heart avoids Isaac and fires 4 blood shots in the cardinal directions when Isaac gets near. Killing the Heart will automatically kill the Mask.
Mask II + 1/2 Heart	93.1	The Mask is invulnerable and moves around erratically, charging at Isaac when he lines up with it. The Heart avoids Isaac and fires 4 blood shots in the ordinal directions when Isaac gets near. Killing the Heart will automatically kill the Mask. If there are more than one 1/2 Heart in the room, they will fire blood shots between each other.
Baby Long Legs	206.0	Runs away from Isaac and frequently spawns Spiders.
Small Baby Long Legs	206.1	Runs away from Isaac and occasionally spawns weaker, slower regenerating Sacks.
Crazy Long Legs	207.0	Chases Isaac, dealing touch damage. Occasionally stops to spit 8 blood shots in all directions.
Small Crazy Long Legs	207.1	Chases Isaac, dealing touch damage. Occasionally stops to spit 4 blood shots in the diagonal directions.
Fatty	208.0	Slowly walks towards Isaac. Occasionally farts, which pushes Isaac and adjacent enemies away.
Pale Fatty	208.1	Slowly walks towards Isaac. Occasionally farts and shoots 6 blood shots in all directions. Has a chance to turn into a Blubber upon death.
Flaming Fatty	208.2	Slowly walks towards Isaac. Occasionally farts, which pushes Isaac and adjacent enemies away and spawns a damaging flame. Has a chance to leave behind a damaging flame upon death.
Fat Sack	209.0	Slowly walks towards Isaac. Occasionally leaps off-screen and attempts to land on Isaac, leaving a puddle of Red Creep and shooting 6 blood shots in all directions where it lands. Has a chance to turn into a Blubber upon death.
Blubber	210.0	Walks around aimlessly and randomly spews a cluster of blood shots in all directions. Has a chance to turn into a Half Sack when killed.
Half Sack	211.0	Wanders around aimlessly and leaves a trail of Red Creep.
Conjoined Fatty	257.0	Slowly walks towards Isaac. Occasionally pauses to fart out a line of damaging Green Creep towards Isaac. Chance to turn into a regular Fatty upon death.
Blue Conjoined Fatty	257.1	Slowly walks towards Isaac and occasionally farts out a homing Ipecac shot at Isaac.
Stoney	302.0	Chases Isaac and blocks tears, but does not deal contact damage. Temporarily pauses in exhaustion after a certain amount of time. Invulnerable; dies when the room is cleared.
Cross Stoney	302.10	Chases Isaac and shoots 4 tears vertically and diagonally like a Cross Stone Shooter. Dies when the room is cleared. Only appears in Aprils Fool (challenge #32) as replacements to regular Stoneys.
Bubbles	806.0	Slowly walks towards Isaac, firing back shots upon taking damage. Occasionally farts, which pushes Isaac and adjacent enemies away and creates a chaotic burst of shots. Creates a geyser of water shots upon death.
Quakey	823.0	Walks slowly toward Isaac, occasionally attempting to jump on Isaac, shooting out 8 rock shots when it hits the ground and causing rocks to fall from the ceiling.
Big Bony	830.0	Walks slowly toward Isaac, and will occasionally fire a bone that bounces around the room for a few moments. The bone can be broken if shot enough.
Gutted Fatty	831.0	Slowly lumbers around the room, occasionally spawning Festering Guts. Its eyes dislocate as it takes damage, which are invincible and follow the Gutted Fatty but chase Isaac if he gets close to them. Creates a geyser of blood projectiles upon death.
Gutted Fatty Eye	831.10	Invulnerable enemy spawned by Gutted Fatties. Hovers around their correlating Gutted Fatty unless Isaac draws near, after which it will chase Isaac, blocking tears and dealing contact damage.
Peeping Fatty	835.0	Has two indestructible Peeping Fatty Eyes that are out of their sockets but attached by muscles. Wanders around the room randomly, or toward Isaac if its eyes see him. Occasionally farts and fires a radial burst of 6 blood shots.
Peeping Fatty Eye	835.10	Invulnerable enemy attached to a Peeping Fatty. Follows Isaac when in line of sight, blocking tears and dealing contact damage.
Bloaty	879.0	Lumbers around, occasionally spitting green shots and a line of damaging green creep in a random direction.
Vis Fatty	886.0	Spawns with a Fetal Demon attached to it and slowly walks towards Isaac. Will occasionally fart, briefly pushing the demon away and spawning creep around itself and the demon. If the demon is killed first, the Fatty will shoot out Brimstone in the diagonal direction closest to Isaac. It will then fly around the room diagonally, bumping off of walls and tall blocks, all while continuously firing Brimstone behind it.
Fetal Demon	886.1	Usually encountered tethered to Vis Fatties. When tethered it makes short lunges towards Isaac if he gets close. If the Vis Fatty is killed or when encountered alone, it will chase Isaac, similarly to Gemini's Suture.
Shady	888.0	Walks slowly toward Isaac, occasionally firing a shot that creates shots perpendicular to itself while traveling and splits into a ring of shots upon hitting a wall or obstacle. Also occasionally jumps, creating lines of explosions in the cardinal directions. One of the few enemies that utilize Damage Scaling.
Death's Head	212.0	Invulnerable enemy that moves diagonally around the room, dealing contact damage. Dies when the room is cleared.
Dank Death's Head	212.1	Moves diagonally around the room, dealing contact damage. Needs to be killed to complete the room.
Cursed Death's Head	212.2	Invulnerable enemy that moves diagonally around the room, dealing contact damage. If Isaac enters its purple aura, he will be inflicted with fear and be temporarily unable to shoot. Dies when the room is cleared.
Brimstone Death's Head	212.3	Invulnerable enemy that moves diagonally around the room, pausing to fire a Brimstone laser when Isaac lines up with it in the cardinal directions. Dies when the room is cleared.
Redskull	212.4	Moves diagonally around the room, creating a ring of fire around itself if Isaac gets close to it. Can be killed, but also dies when the room is cleared.
Flesh Death's Head	286.0	Moves diagonally around the room, dealing contact damage. Releases 6 blood shots in all directions upon death. Can be killed, but also dies when the room is cleared.
Dusty Death's Head	887.0	Invulnerable enemy that moves across the room in a waving motion in large quantities. Dies when the room is cleared.
Ultra Death Head	951.42	Invulnerable enemy spawned by Ultra Death that moves across the room in a waving motion in large quantities as a part of one of his attacks. Dies upon the completion of the attack.
Mom's Hand	213.0	Falls from the ceiling. If it lands on Isaac, it deals damage and teleports him back to the spawn room of the floor. Entering a room containing Mom's Hand will warn Isaac with Mom's laugh.
Mom's Dead Hand	287.0	Falls from the ceiling. Upon landing, it spawns several rock waves that travel outwards. Spawns several spiders upon death. Entering a room containing Mom's Dead Hand will warn Isaac with Mom's laugh.
Level 2 Fly	214.0	Flies toward Isaac erratically, dealing contact damage.
Full Fly	249.0	Flies toward Isaac erratically, dealing contact damage. Releases 6 bullets in all directions upon death.
Level 2 Willo	838.0	Orbits enemies and shoots tears at Isaac. If the enemy it is orbiting dies, it will orbit another enemy. However, if all enemies are dead, it will chase Isaac, while still occasionally shooting at Isaac.
Level 2 Spider	215.0	Crawls around the room erratically, following Isaac and dealing contact damage. Can jump small distances.
Ticking Spider	250.0	Crawls around the room erratically, following Isaac and dealing contact damage. Can jump small distances. Explodes upon death.
Migraine	869.0	Crawls around the room erratically, following Isaac and dealing contact damage. Can jump small distances. Releases multiple Troll Bombs upon death.
Dip	217.0	Slowly dashes in random directions, dealing contact damage.
Corn	217.1	Quickly dashes in random directions, dealing contact damage.
Brownie Corn	217.2	Quickly dashes in random directions, dealing contact damage.
Big Corn	217.3	Quickly dashes in random directions, dealing contact damage. Shoots one piece of corn upon death.
Drip	870.0	Quickly rolls around in diagonal directions, dealing contact damage.
Wizoob	219.0	Disappears, then appears near Isaac and spits a cluster of spectral tears at him.
Red Ghost	285.0	Disappears, then reappears near Isaac and fires a brimstone laser.
Squirt	220.0	Dashes towards Isaac and deals contact damage. Spawns 2 Dips upon death.
Dank Squirt	220.1	Dashes towards Isaac and deals contact damage, creating slowing black creep. Spawns 2 Clots upon death.
Hardy	826.0	Dashes toward Isaac and deals contact damage creating rock projectiles when it hits a wall/obstacle. It spawns more rock projectiles the more times it crashes into obstacles, dying after doing so a third time.
Splurt	871.0	Dashes towards Isaac twice and deals contact damage. Spawns 2 Drips upon death.
Cod Worm	221.0	Stationary enemy that hides in a shell and spews a burst of blood shots if shot at. Only vulnerable when it pops its head out.
Oob	224.0	When Isaac lines up with it horizontally, it charges across the room once. When Isaac is not horizontal to it, it spawns Brains.
Black Maw	225.0	When Isaac lines up with it horizontally, it charges in his direction and then doubles back, charging back to its original position. When Isaac is not horizontal to it, it spawns Leeches. Explodes when it dies.
Skinny	226.0	Slowly walks towards Isaac, leaving short-lasting Red Creep behind itself.
Rotty	226.1	Slowly walks towards Isaac, leaving short-lasting Red Creep behind itself. Spawns a Bony or two Attack Flies upon death.
Crispy	226.2	Slowly walks towards Isaac, but increases in speed as they take damage. Constantly passively takes damage.
Bony	227.0	Wanders around the room and throws a bone at Isaac when he is in sight.
Holy Bony	227.1	Wanders around the room, throwing a bone at Isaac when he is in sight. The thrown bone leaves behind a blue flame that deals contact damage, blocks Isaac’s shots, and despawns after some time.
Black Bony	227.1	Wanders around the room and throws three bones in a row at Isaac when he is in sight. Explodes upon death.
Revenant	841.0	Slowly wanders around the room, stopping to fire a large line of fire at the player.
Quad Revenant	841.1	Wanders around the room slowly, stopping to fire lines of flames in the cardinal or ordinal directions, rotating in an attempt to hit Isaac.
Maze Roamer	890.0	Wanders around the room and shoots an eyeball at Isaac when he is in sight. Has a clone of itself on the other side of the room that mimics its movement and shots. If one dies, the other starts actively pursuing Isaac.
Homunculus	228.0	Starts attached to the wall or an obstacle. After a while, it detaches, shooting 6 blood shots in all directions, leaving a puddle of Red Creep and chasing Isaac. If it dies while still attached, it will still leave a puddle of Red Creep.
Begotten	251.0	Starts attached to the wall or an obstacle. After a while, it detaches, firing 6 blood shots in all directions, turning the room dark, becoming invisible and chasing Isaac. Briefly becomes visible upon getting hit.
Tumor	229.0	Moves around the room diagonally, occasionally firing 6 blood shots in all directions. Fires more often upon getting damaged.
Planetoid	229.1	Moves around the room diagonally, occasionally firing blood shots that orbit itself. Fires more shots and has a chance to send its ring of shots outward upon taking damage.
Camillo Jr.	230.0	Moves around the room diagonally, occasionally firing Technology lasers towards Isaac. Fires more often upon getting damaged.
Psy Tumor	253.0	Moves around the room diagonally, occasionally firing 6 homing shots in all directions. Fires more often upon getting damaged.
Poofer	892.0	Slowly floats toward Isaac, swells up and fire 6 blood shots in all directions upon taking damage. Explodes upon death, healing nearby enemies and leaving a big puddle of red creep.
Nerve Ending	231.0	Static enemy which acts as a meat shield.
Nerve Ending 2	231.1	Static enemy which whips at Isaac if he gets too close.
Bishop	805.0	Shields all enemies in the room, preventing them from taking damage. Fires shots in the cardinal directions when it takes damage.
One Tooth	234.0	Follows Isaac and periodically dashes towards him when it gets close. Deals contact damage.
Fat Bat	258.0	Slowly flies towards Isaac. Tries to align itself diagonally to Isaac and shoots at him when in that alignment.
Gurgling	237.0	Charges towards Isaac when he lines up with them, leaving a trail of Red Creep and shooting 6 blood shots.
Goat	891.0	Wanders around the room. Occasionally moves toward Isaac, either firing blood shots at him or charging if he lines up on either side of it.
Black Goat	891.1	Wanders around the room. Occasionally moves toward Isaac, either firing blood shots at him or charging if he lines upon either side of it. Can also fire thin Brimstone lasers in the cardinal directions, along with all other Black Goats in the room.
Cultist	885.0	Creates an indestructible, homing Purple Ball at the start of the room and follows it around, occasionally leaving it to revive enemies that have died in the current room.
Blood Cultist	885.1	Wanders around the room and fires a line of blood shots and creep if Isaac is on either side of it. Can summons bone traps that temporarily ensnare Isaac if he walks into them.
Grub	239.0	Erratically moves around the room like Larry Jr. and charges at Isaac when he gets within its line of sight. Spawns Maggots, Chargers, or Spitties upon death, one for each of its segments.
Wall Creep	240.0	Crawls along walls to try to line up with Isaac and shoots three blood shots in a line.
Soy Creep	240.1	Slowly crawls along walls to try to line up with Isaac and shoots a stream of shots seemingly affected by Soy Milk.
Tainted Soy Creep	240.3	Slowly crawls along walls to try to line up with Isaac and shoots a 4 diagonal streams of Soy Milk shots.
Rage Creep	241.0	Slowly crawls along walls to try to line up with Isaac and shoots a Brimstone laser.
Blind Creep	242.0	Randomly crawls along walls and shoots three spread blood shots.
The Thing	304.0	Crawls along a wall and attempts to line up with Isaac, then spits a line of damaging Red Creep.
Round Worm	244.0	Pops out of the ground in random locations and spits a blood shot at Isaac if he is in sight.
Tube Worm	244.1	Pops out of the ground in random locations and fires a long-range spray of arcing shots where Isaac will be.
Tainted Round Worm	244.2	Pops out of the ground in random locations alongside several tail ends. The head fires a large blood shot that splits into a radial burst of 8 blood shots, while the tail ends shoot normal blood shots.
Tainted Tube Worm	244.3	Pops out of the ground in random locations, spitting 4 explosive shots towards Isaac.
Night Crawler	255.0	Pops out of the ground in random locations and fires four short-range shots that spiral outwards if Isaac is in sight.
Roundy	276.0	Pops out of the ground in random locations, creating a small rock wave. Fires an explosive Ipecac shot at Isaac if he is in sight.
Ulcer	289.0	Pops out of the ground in random locations and spawns a Dart Fly if Isaac is in sight. Fires a blood shot after spawning 6 Dart Flies.
Fire Worm	825.0	Pops out of the ground in random locations in the lava and fires one flame at Isaac.
Mole	829.0	Burrows towards Isaac and jumps out the ground to fire 3 blood shots at him.
Tainted Mole	829.1	Dig towards Isaac and release a ring of rock waves. Fires 3 blood shots at Isaac 4 times.
Lil' Haunt	260.0	Floats toward Isaac and occasionally fires a blood shot at him, predicting his movements.
Polty	816.0	Picks up and throws rocks and props at Isaac.
Kineti	816.1	Uses telekinesis to pick up and throw rocks and obstacles at Isaac.
Dust	882.0	Follows Isaac, and is only visible when close to Isaac. Will begin to speed up when they are visible. Teleports away after taking enough damage.
Dukie	288.0	Flies around the room diagonally, occasionally spitting out 1-2 Dart Flies.
Meatball	290.0	Slides around the room. If Isaac is in sight, it will stop to spew a fountain of short-range blood shots in all directions or to spit a line of damaging Red Creep towards Isaac. Spawns a Host upon death.
Ministro	305.0	Hops around randomly and hop towards Isaac when he gets close, occasionally spitting out a cluster of disorganized shots.
Fistuloid	308.0	Flies towards Isaac in an erratic waving motion, periodically firing a blood shot towards Isaac that also knocks itself back. Upon death, fires a worm that flies off screen.
Fly Trap	873.0	Floats towards Isaac, with 3 Attack Flies circling around it. Coughs up additional Attack Flies and releases gas to launch the Attack Flies outwards.
Poot Mine	875.0	Creates a gas cloud and propels itself away from Isaac when it gets hit non-consecutively. Explodes on death, detonating all the gas clouds it created.
Bombgagger	844.0	Spits up a Giga Bomb and runs away from it.
Flesh Maiden	880.0	Vaguely flies towards Isaac in curved swooping motions.
Morningstar	863.0	Floats toward Isaac to deal contact damage while Isaac is moving, gaining speed the longer Isaac continues moving. Stops moving when Isaac stops moving.
Needle	881.0	Pops out of the ground and lunges towards Isaac, dealing contact damage.
Pasty	881.1	Pops out of the ground and lunges toward Isaac, dealing contact damage and firing four shots in the ordinal directions.
Fissure	815.0	Jumps out of pits and bounces around the room. Spawns endlessly from pits until room clear. Do not need to be killed to clear room.
Portal	306.0	Spawns various enemies from the current floor until it either vanishes or is killed.
Lil Portal	306.1	Spawns fly and spider enemies until it is destroyed.
Henry	837.0	Flushes itself away shortly after Isaac enters the room.
Stone Grimace	42.0	Stationary and invulnerable monster that occasionally fires a blood shot at Isaac. Stops firing when room is cleared.
Vomit Grimace	42.1	Stationary and invulnerable monster that occasionally fires an Ipecac shot at Isaac. Stops firing when room is cleared.
Triple Grimace	42.2	Stationary and invulnerable monster that occasionally fires a triple shot at Isaac. Stops firing when room is cleared.
Stone Eye	201.0	Stationary and invulnerable monster that constantly rotates and fires a flickering Technology laser. Stops firing when the room is cleared.
Constant Stone Shooter	202.0	Stationary and invulnerable monster that continuously fires shots in a single direction.
Cross Stone Shooter	202.10	Stationary and invulnerable monster that continuously fires shots in four directions, alternating between cardinal and ordinal.
Brimstone Head	203.0	Stationary and invulnerable monster that fires Brimstone beams in a specific direction.
Gaping Maw	235.0	Stationary and invulnerable monster that sucks Isaac towards it, along with Isaac's tears and enemy projectiles.
Broken Gaping Maw	236.0	Stationary and invulnerable monster that sucks Isaac towards it, along with Isaac's tears and enemy projectiles. Alternates between active and inactive every couple of seconds. Has a stronger attraction power than a regular Gaping Maw.
Quake Grimace	804.0	Stationary and invulnerable monster that jumps and fires a line of rocks in one direction upon landing.
Bomb Grimace	809.0	Stationary and invulnerable monster that keeps a single Throwable Bomb spawned.
Peep Eye	68.1	Invulnerable enemy that floats diagonally over obstacles and bounces off of walls, blocking tears and dealing contact damage. Spawned by Peep as apart of his fight.
Bloat Eye	68.11	Invulnerable enemy that floats diagonally over obstacles and bounces off of walls, blocking tears and dealing contact damage. Spawned by The Bloat as apart of his fight.
Mockulus	864.0	Invulnerable enemy that rapidly floats diagonally over obstacles and bounces off of walls, blocking tears and dealing contact damage. They can only move while Isaac is shooting.
Poky	44.0	Slides around the room aimlessly, damaging Isaac by contact. Disappears when the room is cleared.
Slide	44.1	Quickly slides towards Isaac when he gets in its line of sight, then moves slowly back to its original position. Cannot be destroyed.
Wall Hugger	218.0	Moves around the room like Guts, damaging Isaac by contact. Cannot be destroyed.
Grudge	877.0	Quickly slides towards Isaac when he gets in its line of sight. Cannot be destroyed.
Ball and Chain	893.0	Spike balls that rotate at the end of a chain attached to an obstacle. If the obstacle is destroyed, the ball will fly free around the room for a while.
Spikeball	852.0	Spike balls that fly in a line either horizontally or vertically, bouncing off walls and obstacles.
Singe's Ball	915.1	Spawned exclusively as apart Singe's boss fight and used in his attacks. They can be pushed around and launched with explosions.
Pitfall	291.0	Invulnerable and stationary enemy which Isaac falls into when walked over, taking damage and popping back out after a short delay.
Suction Pitfall	291.1	Invulnerable and stationary enemy which sucks Isaac towards itself. Isaac falls into it when walked over, taking damage and popping back out after a short delay.
Teleport Pitfall	291.2	Invulnerable and stationary enemy which Isaac falls into when walked over, taking damage and popping back out at a random location after a short delay.
Death Scythe	66.10	Stays stationary for a few seconds, then homes in on Isaac.
Ultra Death Scythe	951.41	Stays stationary for a moment, then travels in straight lines towards Ultra Death.
Corn Mine	295.0	Goes off when destroyed or after some time, then releases a cloud of poisonous gas and fires corny shots in eight directions.
Siren Minion	3.220	Spawned in automatically charmed by The Siren. Orbits the boss and fires projectiles towards Isaac.
Siren Helper	966.0	Spawned in by The Siren and takes the form and control of all of her charmed familiars.
Dark Ball	404.1	Floats towards Isaac, doing contact damage.
Purple Ball	409.1	Floats towards Isaac, doing contact damage.
Visage Plasma	903.20	Floats in diagonal directions, doing contact damage. Spawned by The Visage and used in its phase 3 attacks.
Ultra Pestilence Fly Ball	951.23	Floats towards Isaac, doing contact damage and spawning Ultra Pestilence Flies upon taking damage.
Ultra Greed Coin (Spinner)	293.0	Spins around the room, dealing contact damage.
Ultra Greed Coin (Key)	293.1	Spins on itself and opens a golden door around the room if not destroyed, spawning hordes of Greed Gapers.
Ultra Greed Coin (Bomb)	293.2	Spins on itself and explodes with a large radius if not destroyed.
Ultra Greed Coin (Heart)	293.3	Spins on itself and heals Ultra Greed for 13.125 HP each if not destroyed.
Dummy	964.0	Only encounterable through Debug Console, it is immobile, harmless, and used to track Isaac's damage.

Champions

See the champions page.

Monster Replacements

Some monsters have a chance to be replaced with other monsters when they spawn, but only at room entry. Some replacements only occur on certain floors.

(Disclaimer: Chances are approximate!)

Rebirth

Base Monster	Replacement	Chance
		10%
		1%
		6%
		6%
		5%
		5%
		5%
		1%
		10%
		1%
		10%
		6% (Utero only)
		1%
		10% ( Not in Chapter 1)
		10%
		5%
		1%
		6%
		10%
		6%
		6%
		1%
		6%
		1%
		6%
		6%

Afterbirth

Base Monster	Replacement	Chance	Notes
		60%	Exclusive to Burning Basement
		60%	Exclusive to Burning Basement Only a single Burning Basement room contains a Pale Fatty, making it a very unusual replacement to witness.
		60%	Exclusive to Burning Basement
		60%
		50%	Exclusive to Flooded Caves
		50%	Exclusive to Flooded Caves
		50%
		50%	Exclusive to Flooded Caves
		50%	Exclusive to Dank Depths
		50%	Exclusive to Dank Depths
		50%	Exclusive to Dank Depths
		50%	Exclusive to Scarred Womb
		50%	Exclusive to Scarred Womb
		50%	Exclusive to Scarred Womb

Afterbirth+

Base Monster	Replacement	Chance	Notes
		10%
		20%
		20%	Exclusive to Chapter 2
		20%
		20%
		20%
		10%
		20%
		20%
		40%	Exclusive to Burning Basement Rottys do not appear in any Burning Basement room layouts, but can still be replaced regardless.
		50%	Exclusive to Flooded Caves Dank Chargers do not appear in any Flooded Caves room layouts, but can still be replaced regardless.
		20%	Exclusive to Aprils Fool challenge

Repentance

Base Monster	Replacement	Chance
		1.66%
		1.66%

Bugs

Bug!	PS 4 Some Champion enemies that turn into another enemy when killed (Gurgle turning into Splasher for instance) become invisible.

The Binding of Isaac: Rebirth

• Achievements
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