Ascent

The Ascent is a special sequence begun by obtaining Dad's Note from the special versions of the Mausoleum/Gehenna II. These floors can be accessed by opening the special door in the starting room of the Depths II or its variants. This door appears once Isaac has defeated Mother at least once. It involves going back up through abbreviated versions of every floor previously seen through beams of light. Much like the Backasswards challenge, Isaac begins in the boss room of each floor and must find the beam of light, located in the corresponding starting room.

These abbreviated versions contain the same Treasure Rooms and Boss Rooms as they did previously, in almost the same condition.

Any trinkets left behind in these rooms, however, will each be transformed into a Cracked Key.

All the other special rooms do not spawn.

Special Red Rooms still have the normal chance to be generated.

Monsters not normally found on the current floor will appear, as well as unique room layouts and new monsters not found anywhere else in the game.

After leaving the Mausoleum II, Isaac will begin taking full heart damage, as would otherwise occur on entering any variant of the Womb or the Corpse.

Entering the Basement I's light beam will take Isaac to Home.

Unique Monsters

This table lists all of the unique monsters that only spawn during the ascent. These enemies are based on normal enemies from the individual pre-ascent chapters they are seen in, but are far tougher.

Entity	ID	Description
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.
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.
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.
Tainted Hopper	29.3	Jumps and twirls around the room, shooting 4 rings of projectiles that increase in size with each shot.
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.
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.
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.
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.
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.
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.
Tainted Mole	829.1	Dig towards Isaac and release a ring of rock waves. Fires 3 blood shots at Isaac 4 times.
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.

Regular Monsters

When the game makes a small mock floor to take the place of each original floor/chapter Isaac descended through before the ascent, it populates each new floor mostly with its pre-ascent chapter-specific enemies. However, the Ascent enemy pools are altered to allow enemies from later floors.

These are the tables of enemies the game spawns to populate its specific ascent mock chapters.

Mausoleum

Entity	ID	Description
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.
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.
Bishop	805.0	Shields all enemies in the room, preventing them from taking damage. Fires shots in the cardinal directions when it takes damage.
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.
Bony	227.0	Wanders around the room and briefly stands still to throw a bone at Isaac when he is in sight.
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.
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.
Candler	833.0	Flies around the room and propels itself by spawning flames.
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.
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.
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.
Death's Head	212.0	Invulnerable enemy that moves diagonally around the room, dealing contact damage. Dies when the room is cleared.
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.
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.
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.
Grudge	877.0	Quickly slides towards Isaac when he gets in its line of sight. Cannot be destroyed.
Kineti	816.1	Uses telekinesis to pick up and throw rocks and obstacles at Isaac.
Lil Portal	306.1	Spawns fly and spider enemies until it is destroyed.
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.
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.
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.
Pon	840.0	Hops around the room, leaving damaging red creep wherever it lands. Upon death, its associated Brainless Knight dies with it.
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.
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.
Revenant	841.0	Slowly wanders around the room, stopping to fire a large line of fire at the player.
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.
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.
Soul Sucker	61.2	Flies slowly towards Isaac. Spawns a vortex that fires four Brimstone beams in the cardinal directions upon death.
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.
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.
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.

Depths

Entity	ID	Description
Wrinkly Baby	38.3	Dashes towards Isaac at high speed and fires three blood shots in his direction once stopped.
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.
Brain	32.0	Slowly crawls around the room, leaving a trail of red creep.
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.
Poison Mind	301.0	Slowly crawls/floats around the room diagonally, leaving a trail of damaging green creep. Explodes upon death.
Baby	38.0	Slowly floats towards Isaac and fires a blood shot at him. Occasionally teleports and reappears elsewhere.
Bony	227.0	Wanders around the room and briefly stands still to throw a bone at Isaac when he is in sight.
Black Bony	227.1	Wanders around the room and stands still to throw three bones in a row at Isaac when he is in sight. Explodes upon death.
Death's Head	212.0	Invulnerable enemy that moves diagonally around the room, dealing contact damage. Dies when the room is cleared.
Dukie	288.0	Flies around the room diagonally, occasionally spitting out 1-2 Dart Flies.
Embryo	77.0	Aimlessly hops around the room, dealing contact damage.
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.
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.
Half Sack	211.0	Wanders around aimlessly and leaves a trail of Red Creep.
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.
Attack Fly	18.0	Red fly that follows Isaac and deals contact damage.
Army Fly	868.0	Chases Isaac, moving along the cardinal directions. Forms a line with other Army Flies in the room. Deals contact damage.
Sucker	61.0	Flies slowly towards Isaac, exploding into 4 shots in the cardinal directions upon death.
Boom Fly	25.0	Flies across the room in straight diagonal lines, dealing contact damage. Explodes upon death.
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.
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.
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.
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.
Guts	40.0	Attaches itself to a wall or obstacle and rolls around it.
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.
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.
Eggy	29.2	Hops aimlessly around the room, spawning slowing white creep wherever it hops. Spawns a group of Swarm Spiders upon death.
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.
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.
Mobile Host	204.0	Acts like the Host, but follows Isaac and deals contact damage.
Knight	41.0	Moves erratically around the room and charges towards Isaac when in line of sight. Can only be damaged with regular tears from behind.
Floating Knight	254.0	Behaves like the Knight but slower, and can fly over all obstacles.
Lil' Haunt	260.0	Floats toward Isaac and occasionally fires a blood shot at him, predicting his movements.
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.
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.
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.
Needle	881.0	Pops out of the ground and lunges towards Isaac, dealing contact damage.
One Tooth	234.0	Follows Isaac and periodically dashes towards him when it gets close. Deals contact damage.
Rotty	226.1	Slowly walks towards Isaac, leaving short-lasting Red Creep behind itself. Spawns a Bony or two Attack Flies 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.
Swarmer	91.0	Slowly floats around the room, spawning several Attack Flies. Spawns Pooters upon taking damage. Spawns a Boom Fly upon death.
Vis	39.0	Randomly wanders around the room. Pauses to charge and fire a Brimstone laser when Isaac gets in its line of sight.
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.
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.
Rage Creep	241.0	Slowly crawls along walls to try to line up with Isaac and shoots a Brimstone laser.
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.
Stone Grimace	42.0	Stationary and invulnerable monster that occasionally fires a blood 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.
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.

Degraded Bosses:

Name	ID	Notes
Dingle	261.0
Fistula	71.0	Medium-form only
The Haunt	260.0

Mines

Entity	ID	Description
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.
Blaster	821.0	Slowly wanders around and occasionally shoots Fly Bombs at Isaac.
Bomb Grimace	809.0	Stationary and invulnerable monster that keeps a single Throwable Bomb spawned.
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.
Bony	227.0	Wanders around the room and briefly stands still to throw a bone at Isaac when he is in sight.
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.
Coal Boy	820.1	Walks toward Isaac and spits hot coals at him, some of which may be Coal Spiders.
Crackle	87.1	Walks toward Isaac, dealing contact damage and spitting fireballs that create lines of fire in the cardinal directions on impact.
Danny	820.0	Walks toward Isaac and spits chaotic bursts of rocks at him, some of which may be Rock Spiders.
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.
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.
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.
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.
Fire Worm	825.0	Pops out of the ground in random locations in the lava and fires one flame at Isaac.
Flesh Maiden	880.0	Vaguely flies towards Isaac in curved swooping motions.
Fly Bomb	819.0	Flies toward Isaac, circling around him as it does. Turn into a tiny Bomb upon death.
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.
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.
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.
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.
Ink	61.3	Flies slowly towards Isaac. Fires four shots in the ordinal directions and leaves a puddle of slowing Black Creep 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.
Mole	829.0	Burrows towards Isaac and jumps out the ground to fire 3 blood shots at him.
Necro	828.0	Stationary enemy that summons unlimited-ranged bones to attack Isaac.
Quake Grimace	804.0	Stationary and invulnerable monster that jumps and fires a line of rocks in one direction upon landing.
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.
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.
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.
Stone Grimace	42.0	Stationary and invulnerable monster that occasionally fires a blood shot at Isaac. Stops firing when room is cleared.
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.

Caves

Entity	ID	Description
Army Fly	868.0	Chases Isaac, moving along the cardinal directions. Forms a line with other Army Flies in the room. Deals contact damage.
Blind Creep	242.0	Randomly crawls along walls and shoots three spread blood shots.
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.
Boom Fly	25.0	Flies across the room in straight diagonal lines, dealing contact damage. Explodes upon death.
Buttlicker	89.0	Can start attached to other Buttlickers and erratically moves around the room, similar to Larry Jr..
Charger	23.0	Slowly moves around the room, charging at Isaac when he 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.
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.
Conjoined Spitty	243.0	Slowly moves around the room, occasionally firing a blood shot from both ends of its body.
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.
Constant Stone Shooter	202.0	Stationary and invulnerable monster that continuously fires shots in a single direction.
Dart Fly	256.0	Flies towards Isaac and attempts to predict his movements. Deals contact damage.
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.
Dukie	288.0	Flies around the room diagonally, occasionally spitting out 1-2 Dart Flies.
Eggy	29.2	Hops aimlessly around the room, spawning slowing white creep wherever it hops. Spawns a group of Swarm Spiders 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.
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.
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.
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.
Half Sack	211.0	Wanders around aimlessly and leaves a trail of Red Creep.
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.
Horf	12.0	Stationary enemy that fires a medium-ranged blood shot at Isaac when he gets in range of them.
I.Blob	15.2	Randomly wanders around the room, firing 8 shots in all directions.
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.
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.
Maggot	21.0	Aimlessly moves around the room, dealing contact damage.
Maw	26.0	Slowly floats towards Isaac, firing a blood shot at him when he is in their range.
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.
Migraine	869.0	Crawls around the room erratically, following Isaac and dealing contact damage. Can jump small distances. Releases multiple Troll Bombs upon death.
Ministro	305.0	Hops around randomly and hop towards Isaac when he gets close, occasionally spitting out a cluster of disorganized shots.
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.
Needle	881.0	Pops out of the ground and lunges towards Isaac, dealing contact damage.
One Tooth	234.0	Follows Isaac and periodically dashes towards him when it gets close. Deals 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.
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.
Red Maw	26.1	Floats quickly towards Isaac and releases 4 blood shots in the cardinal directions upon death.
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.
Spit	61.1	Flies slowly towards Isaac, firing an Ipecac shot towards Isaac upon death.
Spitty	31.0	Slowly moves around the room, occasionally firing a single blood shot forward.
Squirt	220.0	Dashes towards Isaac and deals contact damage. Spawns 2 Dips upon death.
Stone Grimace	42.0	Stationary and invulnerable monster that occasionally fires a blood shot at Isaac. Stops firing when room is cleared.
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.
Sucker	61.0	Flies slowly towards Isaac, exploding into 4 shots in the cardinal directions upon death.
Ticking Spider	250.0	Crawls around the room erratically, following Isaac and dealing contact damage. Can jump small distances. Explodes upon death.
Triple Grimace	42.2	Stationary and invulnerable monster that occasionally fires a triple 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.
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.

Degraded Bosses:

Name	ID
The Duke of Flies	67.0
The Hollow	19.1
Larry Jr.	19.0

Downpour

Entity	ID	Description
Attack Fly	18.0	Red fly that follows Isaac and deals contact damage.
Bloaty	879.0	Lumbers around, occasionally spitting green shots and a line of damaging green creep in a random direction.
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.
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.
Deep Gaper	811.0	Emerges from the floor once all previous enemies have been killed, then proceeds to chase Isaac. Deals contact damage.
Drip	870.0	Quickly rolls around in diagonal directions, dealing contact damage.
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.
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.
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.
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.
Lil' Haunt	260.0	Floats toward Isaac and occasionally fires a blood shot at him, predicting his movements.
Mullighoul	817.1	Wanders around the room, avoiding Isaac and spawning Willos if he gets close. Spawns 1-2 Willos upon death.
Polty	816.0	Picks up and throws rocks and props at Isaac.
Prey	817.0	Wanders around the room, avoiding Isaac and spawning Small Leeches if he gets close. Spawns 3 Small Leeches upon death.
Small Leech	810.0	Chases Isaac continuously, not stopping at walls. Able to swim over gaps.
Splurt	871.0	Dashes towards Isaac twice and deals contact damage. Spawns 2 Drips upon death.
Strider	814.0	Erratically swims around the room. If it sees Isaac, it chases him, trying to deal contact damage.
Sub Horf	812.0	Stationary enemy that spins and fires shots while being moved around or knocked back.
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.
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.
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.

Basement

Entity	ID	Description
Army Fly	868.0	Chases Isaac, moving along the cardinal directions. Forms a line with other Army Flies in the room. Deals contact damage.
Attack Fly	18.0	Red fly that follows Isaac and deals 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.
Constant Stone Shooter	202.0	Stationary and invulnerable monster that continuously fires shots in a single direction.
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.
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.
Dip	217.0	Slowly dashes in random directions, dealing contact damage.
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.
Fatty	208.0	Slowly walks towards Isaac. Occasionally farts, which pushes Isaac and adjacent enemies away.
Flaming Hopper	54.0	Quickly hops around the room, doing contact damage. Covers a larger distance than the regular Hopper.
Fly	13.0	Hovers in place. Does not deal contact damage and is harmless, but can turn into Pooters if they stay around Poop.
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.
Full Fly	249.0	Flies toward Isaac erratically, dealing contact damage. Releases 6 bullets in all directions upon death.
Gaper	10.1	Walks towards Isaac, dealing contact damage. Usually turns into a Pacer or a Gusher upon death.
Grilled Clotty	15.3	Quickly and randomly wanders around the room, firing four flame shots in the cardinal directions at a slight angle.
Gusher	11.0	Walks aimlessly around the room, occasionally firing a short-ranged blood shot.
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.
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.
Horf	12.0	Stationary enemy that fires a medium-ranged blood shot at Isaac when he gets in range of them.
Ink	61.3	Flies slowly towards Isaac. Fires four shots in the ordinal directions and leaves a puddle of slowing Black Creep upon death.
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.
Lil' Haunt	260.0	Floats toward Isaac and occasionally fires a blood shot at him, predicting his movements.
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.
Migraine	869.0	Crawls around the room erratically, following Isaac and dealing contact damage. Can jump small distances. Releases multiple Troll Bombs upon death.
Ministro	305.0	Hops around randomly and hop towards Isaac when he gets close, occasionally spitting out a cluster of disorganized shots.
Moter	80.0	Follows Isaac, similar to Attack Flies. Deals contact damage. Splits into 2 Attack Flies upon death.
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.
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.
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.
Para-Bite	58.0	Moves towards Isaac, dealing contact damage. Can burrow underground and reappear elsewhere.
Pooter	14.0	Slowly drifts toward Isaac, occasionally firing a single blood shot at him. Does not deal contact damage.
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.
Ring Fly	222.0	Gathers with any other Ring Flies in the room. These flies orbit around themselves while following Isaac. Deals contact damage.
Rotty	226.1	Slowly walks towards Isaac, leaving short-lasting Red Creep behind itself. Spawns a Bony or two Attack Flies upon death.
Round Worm	244.0	Pops out of the ground in random locations and spits a blood shot at Isaac if he 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.
Soul Sucker	61.2	Flies slowly towards Isaac. Spawns a vortex that fires four Brimstone beams in the cardinal directions upon death.
Squirt	220.0	Dashes towards Isaac and deals contact damage. Spawns 2 Dips upon death.
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.
Sub Horf	812.0	Stationary enemy that spins and fires shots while being moved around or knocked back.
Sucker	61.0	Flies slowly towards Isaac, exploding into 4 shots in the cardinal directions upon death.
Ticking Spider	250.0	Crawls around the room erratically, following Isaac and dealing contact damage. Can jump small distances. Explodes upon death.
Vis	39.0	Randomly wanders around the room. Pauses to charge and fire a Brimstone laser when Isaac gets in its line of sight.
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.

Degraded Bosses:

Name	ID
Baby Plum	908.0
Dingle	261.0
The Duke of Flies	67.0
Gemini	79.0
Gish	43.1
The Husk	67.1
Mega Fatty	264.0
Monstro	20.0
Steven	79.1
Widow	100.0

Notes

If any variant floors were encountered during descent, all floors of the Ascent will still be the original ones. For example, if the second floor on a run was the Cellar II or the Burning Basement II, during the Ascent, it will be replaced by the Basement II regardless. This includes alternate chapters, such as the Downpour, and so on.
- However, it's still possible to access them through the use of Debug Console.
Isaac won't encounter any curses during the Ascent, except Curse of the Labyrinth if it was on the original floor.
- When encountering Curse of the Blind, it may be a good idea to skip boss and treasure room items, as they will be revealed during the Ascent.
- XL floors in the Ascent will contain both Treasure Rooms from the original floor.
Red Treasure Rooms found through the Red Key during the original run will automatically show up during the Ascent, and will be adjacent to normal rooms. These doors do not require keys to open.
Any unopened Treasure Rooms on previous floors will still be locked during the Ascent.
- If these skipped Treasure Rooms are entered during the ascent, they will contain different items. This is best viewed with the effect of Dream Catcher.
- This also means a strategy is to skip Treasure Rooms early in a run to spawn a Planetarium, and then get the skipped Treasure Room items during the Ascent. However, there's no need to keep doing it after encountering a Planetarium, since the probability to encounter it will stay at 1%.
Angel Rooms and Devil Rooms will have different contents than on the original path.
- Since the Boss Rooms have already been cleared during descent, Devil Rooms and Angel Rooms won't open during the Ascent, and can only be accessed with teleport effects.
- The special Angel Room Shops generated by The Stairway will also have different contents.
During the Ascent, both items in a double item Treasure Room are visible.
Items and trinkets that activate on entering the floor, such as Maggy's Faith, will trigger each time Isaac ascends a floor.
If pickups were transported to another floor from the Treasure or Boss Room by Myosotis, their copies will remain in those rooms and can be encountered during the Ascent. Affected trinkets still transform into Cracked Keys, potentially allowing you to gain large amounts of Cracked Keys.
- Myosotis will work on the Ascent, and can be used to bring an additional pickup if holding a Cracked Key.
In each floor, after exploring all normal rooms, using Teleport 2.0 will teleport Isaac to the Angel Room/Devil Room, since Secret Rooms and Super Secret Rooms will not spawn.
If a floor is restarted, which can be accomplished through using Forget Me Now or by finding a Red 5-pip Dice Room, the following effects will happen:
- No dream animations will be shown when restarting.
- The regenerated floor will still be an Ascent floor, not a descent floor.
- If the floor was an XL one, the regenerated floor will also be XL.
- If the Treasure Room was skipped during descent, and during the Ascent its contents were seen, after restarting it will contain different items.
- All Cracked Keys in either the Boss Room or the Treasure Room will remain there, even if they were used before restarting.
The I AM ERROR room can be reached during the ascent. I AM ERROR rooms will mimic the layout that they had corresponding to the floor. Rather than containing a trapdoor, they will contain a beam of light leading up to the next floor.
Entering an I AM ERROR room in Gehenna II (before the Ascent) takes Isaac to the starting room of the floor.
No consumable voice lines will be spoken during the Ascent.
Jacob and Esau will overlap one other when ascending to a new floor. This effect stops upon pressing the Swap key or entering a new room.
During the descent, it is recommended to leave any abandoned Trinkets in Treasure Rooms or Boss Rooms, so that the resulting Cracked Keys can be used during the Ascent, which could potentially create special rooms containing items or other useful pickups.
If the Boss Music would play, it plays the Boss Music for the alternate path rather than the Boss Music for the main path. One way to make Boss Music play is to find an Angel Room by using a Red Key/Cracked Key.
If a Boss is not fought during the descent (e.g. if it was skipped using We Need To Go Deeper!), the Boss Room will still be empty during the Ascent.
Portals to The Void that spawn after the Mom fight will still appear in the boss room during Ascent, however they will be permanently closed.

Dialogue

At various points during the Ascent, arguments between Isaac's parents can be heard, shedding some light on the fractured state of Isaac's family.

Stage	Dialogue	Audio
At the start of the Mausoleum II	Dad: "I spent it, it's gone. Just get over it!" Mom: "What do you mean, what do you mean it's gone? How could you have spent our savings?!"
At the start of the Depths I / Mines II	Mom: "He's self-destructive and disturbed, just like his father! Look at who he has to look up to! ...And you're drunk again, aren't you?" Dad: "Shut up, Maggy! SHUT! UP! You just keep pushing me like this, I'm leaving!" Mom: "Good! LEAVE! We'll be fine without you! Abandon us like you abandoned yourself..."
At the start of the Caves I / Downpour II	Mom: "You need to repent. You need to confess your sins, and become saved! Let His light inside you! CLEANSE YOUR SOU-" Dad: "You. Are. INSANE. You are taking this too far. Can't you hear how you sound!?" Mom: "Pray with me... Pray for your salvation! Come, pray with us, Isaac..."
At the start of the Basement I	(The sound of a door opening and footsteps are heard) Mom: "Where are you going?! Wait! We need you! Your son NEEDS you!" Dad: "I'm doing more harm than good. I just can't do this anymore, I'm sorry." Mom: "PLEASE! PLEASE DON'T LEAVE US...!!" Dad: "I'm sorry, Isaac..."

Trivia

The Ascent is referred to as "backwards" in the sequence's rooms file.
According to an interview with _Kilburn, the tainted enemies were designed with inspiration from eternal champion monsters in The Binding of Isaac: Eternal Edition.
Great Gideon can be seen in its boss room during the Ascent. However, since he was already defeated on the way down, he will be deactivated.
- Even if he was encountered in the Ashpit during the normal descent, he will still appear in the Mines during the Ascent.
- He can still be destroyed by using the Chaos Card, to reveal the unique 1x2 Crawl Space.
- If he was previously destroyed with the Chaos Card before the ascent, he will be missing during the ascent.
What sounds like a reversed version of Genesis Retake Light can be heard playing during the Ascent, and as the ascent progresses, more instruments are added to it based on the floors Isaac ascends through.
- The Mausoleum adds a crunchy, electric bass line.
- The Depths adds occasional guitar riffs and a unique composition.
- The Mines adds a drum line and metal clanking sounds.
- The Caves adds a standard bass line.
- The Downpour adds a fuller guitar line with an echo effect.
- The Basement adds a full drum line.