Abyss

Abyss is an unlockable 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, up to a maximum of 64, after which creating more will replace older locusts.
  - This limit is shared with blue flies and blue spiders.
- The locusts loosely follow Isaac similarly to regular blue flies, 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 locust with arcs of electricity that deal 0.1 damage per tick.
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 onto 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 Isaac's 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.

BFFS! / Hive Mind: Increases the locusts' size and damage by 25%.
- These two items do not stack.
Book of Virtues: Spawns wisps in the form of black-glowing flies with extra HP, that do not fire tears.
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 / Box of Friends: Does not affect locusts.
Ipecac: Locusts will only gain +2 damage.
Sacrificial Altar: Locusts can be sacrificed for items.
Tainted Jacob / Tainted Lazarus: Locusts will disappear when changing between the 2 forms, and will not return when switching back.
Void: If Void consumes Abyss, the latter will take priority and using Void to consume another item pedestal will generate a locust. Even consuming active items will generate a locust, and Void will not copy that active item's effect. This essentially causes Void to act identically to Abyss, albeit requiring 2 more charges per use.

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`, Ipecac locusts are supposed to explode. This never happens in game; Ipecac only gives a locust that deals slightly more damage and poisons enemies.

↑ 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.