Abyss

Abyss is an activated item added in The Binding of Isaac: Repentance.

Effects[]

When used, destroys all items on item pedestals in the room and gives Isaac a unique red locust familiar for each item destroyed.
- These locusts are permanent once created, except that there are a maximum of 64, after which creating more will replace older locusts.
  - This limit is shared with blue flies and blue spider.
- The locusts loosely follow Isaac around and charge in the direction Isaac is firing until they hit an enemy, a wall, or certain obstacles like key blocks, dealing Isaac's damage per tick (3 times per second).
- The locusts may gain additional effects depending on the item destroyed^[1].

In rooms where there are multiple items to choose from, using Abyss will give only one locust for each item choice/set.
If already at the maximum amount of locusts and presented with multiple non-choice item pedestals, using Abyss will only consume half of the pedestals.
Tainted Apollyon starts with this item in the consumable slot.
- If he dies and is revived as another character (e.g. through Ankh), that character will retain the locusts.
If Abyss is used while Isaac is holding an item above his head, it can still consume the item and grant a locust.
Using Abyss to destroy items in Boss Rush or challenge rooms counts as taking the items and will cause waves of bosses or enemies to start spawning.

120 Volt / Jacob's Ladder: A pale blue, electric locust that is otherwise normal.
Blood of the Martyr: A red locust that deals double damage.
Brimstone: A gray, larger locust that is otherwise normal.
The Common Cold / Scorpio / The Virus: A green locust that poisons enemies.
Cricket's Head: A red locust that is larger and deals triple damage.
Fire Mind: An orange, burning locust that sets enemies on fire.
Halo of Flies: Two gray locusts that deal half damage.
Holy Light: A cyan, glowing locust that occasionally calls down beams of light on enemies they hit that deal 3x Isaac's damage.
The Inner Eye: Three normal locusts.
Ipecac: A large, slow, green locust that deals x1.5 damage and poisons enemies.
Mutant Spider: Four normal locusts.
Number One: A yellow locust that is faster, deals damage more quickly, but has shorter range.
Spoon Bender: A purple locust that homes in on enemies.
Rune Bag: A purple locust that has a chance to drop a rune upon killing an enemy.

BFFS! / Hive Mind: Increases the locusts' size and damage by 25%.
- These two items do not stack.
Death Certificate: Abyss can be used to absorb items without being kicked out of the area, allowing Isaac to instantly gain max locusts if used in a large room with enough items.
Extension Cord: Electricity will flow between Isaac and the locusts.

Baby-Bender: Does not affect locusts.
Book of Virtues: Spawns black glowing fly wisps on the middle ring. The wisps have increased HP, but do not fire. The number of items destroyed does not change the wisps given.
Box of Friends: Does not affect locusts.
Ipecac: Locusts will only gain +2 damage from ipecac.
Sacrificial Altar: Locusts can be sacrificed for items.

The way that Abyss works is similar to how it's described in the Book of Revelation, where locusts emerge from the Abyss and are controlled by Apollyon.
The swirl in Void's appearance is in the opposite direction of Abyss's.
The way the flies summoned by Abyss function is similar to the Flash Version of Isaac

Bug!	According to `locusts.xml`, 120 Volt and Jacob's Ladder locusts are supposed to cause electric arcs, and Ipecac locusts are supposed to explode. This never happens in game.

↑ Unique locusts and the items that give them are defined in locusts.xml. There are 505 items listed in the file, but only the items mentioned actually have their locusts implemented.