Portal

This article is about the enemy. For the item, see Lil Portal. For the chapter, see The Void.

Portals are enigmatic entities that appear on many floors/ only in The Void. They continuously spawn enemies until they are destroyed or spawn a certain number of enemies.

Portals spawn different enemies depending on the floor they appear on.

In The Void, Portals spawn enemies based on the theme of the room they are in.

List of possible spawns

Chapter 1

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.
Pooter	14.0	Slowly drifts toward Isaac, occasionally firing a single blood shot at him. Does not deal contact damage.
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.
Attack Fly	18.0	Red fly that follows Isaac and deals contact damage.
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.
Spider	85.0	Erratically moves around the room. If Isaac gets close to it, it chases him, trying to deal contact damage.
Fatty	208.0	Slowly walks towards Isaac. Occasionally farts, which pushes Isaac and adjacent enemies away.
Dip	217.0	Slowly dashes in random directions, dealing contact damage.
Round Worm	244.0	Pops out of the ground in random locations and spits a blood shot at Isaac if he is in sight.

Chapter 2

Entity	ID	Description
Charger	23.0	Slowly moves around the room, charging at Isaac when he gets in its line of sight.
Boom Fly	25.0	Flies across the room in straight diagonal lines, dealing contact damage. Explodes upon death.
Maw	26.0	Slowly floats towards Isaac, firing a blood shot at him when he is in their range.
Sucker	61.0	Flies slowly towards Isaac, exploding into 4 shots in the cardinal directions upon death.
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.
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.

Chapter 3

Entity	ID	Description
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.
Brain	32.0	Slowly crawls around the room, leaving a trail of Red Creep.
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.
Baby	38.0	Slowly floats towards Isaac and fires a blood shot at him. Occasionally teleports and reappears elsewhere.
Knight	41.0	Moves erratically around the room and charges towards Isaac when in line of sight. Can only be damaged from behind.
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.
Death's Head	212.0	Invulnerable enemy that moves diagonally around the room, dealing contact damage. Dies when the room is cleared.
Bony	227.0	Wanders around the room and throws a bone at Isaac when he is in sight.
Tumor	229.0	Moves around the room diagonally, occasionally firing 6 blood shots in all directions. Fires more often upon getting damaged.

Chapter 4

Entity	ID	Description
Clotty	15.0	Randomly wanders around the room, firing 4 blood shots in the cardinal directions.
Brain	32.0	Slowly crawls around the room, leaving a trail of Red Creep.
Leech	55.0	Quickly charges towards Isaac when he gets in its line of sight.
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.
Para-Bite	58.0	Moves towards Isaac, dealing contact damage. 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.
Mobile Host	204.0	Acts like the Host, but follows Isaac and deals contact damage.

Chapter 5

Entity	ID	Description
Baby	38.0	Slowly floats towards Isaac and fires a blood shot at him. Occasionally teleports and reappears elsewhere.
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.
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.
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.
Wizoob	219.0	Disappears, then appears near Isaac and spits a cluster of spectral tears at him.
Bony	227.0	Wanders around the room and throws a bone at Isaac when he is in sight.
Lil' Haunt	260.0	Floats toward Isaac and occasionally fires a blood shot at him, predicting his movements.

Lil Portal

Lil Portals are entities that only appear in Mausoleum and Gehenna. They continuously spawn fly and spider enemies until they are destroyed. There can be a max of 4 spawned monsters alive at once. Monsters they can spawn include:

Entity	ID	Description
Attack Fly	18.0	Red fly that follows Isaac and deals contact damage.
Sucker	61.0	Flies slowly towards Isaac, exploding into 4 shots in the cardinal directions 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.
Moter	80.0	Follows Isaac, similar to Attack Flies. Deals contact damage. Splits into 2 Attack Flies upon death.
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.
Small Crazy Long Legs	207.1	Chases Isaac, dealing touch damage. Occasionally stops to spit 4 blood shots in the diagonal directions.
Level 2 Fly	214.0	Flies toward Isaac erratically, dealing contact damage.
Level 2 Spider	215.0	Crawls around the room erratically, following Isaac and dealing contact damage. Can jump small distances.
Full Fly	249.0	Flies toward Isaac erratically, dealing contact damage. Releases 6 bullets in all directions upon death.
Swarm Spider	884.0	Very erratically hops toward Isaac in large groups, dealing contact damage.

Lil Portal (Flies Only)

There is a variant of the Lil Portal with the ID 306.1.1 that looks and behaves identically to regular Lil Portals but will only spawn Fly related monsters from its regular pool.

Entrance Portal

A special version of the Portal (dubbed the "Entrance Portal" to avoid confusion) serves as the entrance to The Void. It is found in ???, but can also be found after defeating Mom (5% chance and only if Isaac has 10+ tear damage or 20+ items), Mom's Heart/ It Lives (10% chance), Isaac/ Satan (15% chance), ???/ The Lamb (20% chance), or Mega Satan (50% chance). The Entrance Portal room in ??? gets darker the closer the player is to the portal.

Unlockable Achievements

Black Hole - Defeat 20 Portals.

Notes

Charming a Portal with Mom's Eyeshadow or similar items will cause the Portal to spawn permanently charmed enemies similar to the Friendly Ball.
- As a result, a permanently charmed Death's Head can spawn from charmed Portals on Chapter 3 and remain permanently invulnerable. This is the only known method of charming an invulnerable enemy.
If a portal is spawned in ???, Chest, Dark Room or Home via Debug Console, the Portal will despawn a few seconds before spawning any monster.
If Portals aren't unlocked, certain enemies will spawn in their rooms instead, depending on the floor the room is in. For instance, Frowning Gapers spawn as Portal placeholders on Chapter 1 floors, whereas Vises spawn as Portal placeholders on Chapter 4 floors.
It is often wise to instantly run into portals with orbitals after entering the room, if possible. Catching the small window timeframe for this almost always results in their instant death without any consequences.

Gallery

The room darkening as the player approaches the portal.
The Entrance Portal next to the Chest after defeating Isaac. Notice the distortion effect on the chest.
A portal's idle animation, as found in the game files.

Trivia

Before v1.06.0185, portals continually spawned enemies until they were defeated.
Portals were able to spawn Bosses such as The Haunt on floors such as the Cathedral. This was later removed.
As of Booster Pack #5, Portals will now leave a Purple "blood" splatter when killed by the player. This effect is only for aesthetic purposes. Formerly, they left the generic Red blood splatter.
Lil Portals resemble Warp Zones from Super Meat Boy.