Monsters

Monsters refers to the many antagonistic creatures the player will encounter throughout the game.

Most monsters (with few exceptions) will damage Isaac by either touching him or shooting him with projectiles. Less frequently, monsters will spawn additional, lesser monsters, spread creep, or attempt to affect the player's movement. 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 and drop basic pickups on death. There are also champion versions of most bosses.

There are 196 naturally spawning monsters in total. 40 of them were added in Afterbirth and 21 were added in Afterbirth † (13 were added in Booster Packs). Almost all of these naturally spawning entities are featured in the Bestiary, with the exceptions being the Rag Man's Ragling and Suction Pitfall.

Champions

Some monsters can spawn as a Champion which deviates in coloration and size. The champion's coloration/size denotes which peculiar behaviors and traits it will exhibit. Champions will generally drop a pickup (coinciding with the color of the champion) when killed on normal difficulty. However, in hard mode, the drop rate is reduced to 33%, while in Greed Mode, champions won't drop pickups at all.

Most champions have a visual 15% size increase, inflict full heart damage regardless of chapter, and have double the health of a normal monster. Champions are generally regarded as more dangerous than common monsters.

Champions always deal contact damage, regardless of what monster they are (e.g. a common Mulligan will not deal contact damage, but champion versions will).

The identifying scheme for champion qualities is as follows:

ID	Appearance	Effect	Drop	Rarity	Notes
0	Vivid Red	×2.5 amount of HP.	Heart	Common
1	Dark Yellow	Increased movement speed.	Little battery	Common
2	Strong Lime Green	Leaves green creep as it walks.	Pill	Common
3	Vivid Orange	Attacks cause you to drop coins (like Greed or a Hanger). The number of coins dropped range from 1-3, which take away 2-4 coins in total respectively. No coins are dropped if you don't have any.	Coin	Around 2x rarer than common champions.
4	Vivid Blue	Decreased speed.	3 Blue Flies	Around 2x rarer than common champions.
5	Dark Cyan	Explodes when killed.	Bomb	Common
6	White	Invincible until all other enemies are killed.	Eternal Heart	Around 10x rarer than common champions.	Doesn't appear until entering Template:Stage and its alts, or Template:Stage in Greed Mode.
7	Dark Gray	2/3 health, decreased speed.	Key	Common
8	Transparent White	Tears become spectral tears, and it can move past environmental obstacles (such as pits) that it otherwise couldn't when forced.	Locked Chest	Around 10x rarer than common champions.	Doesn't appear until entering Template:Stage and its alts, or Template:Stage in Greed Mode.
9	Black	Fades in and out of visibility, like a Null.	Red Chest	Around 10x rarer than common champions.	Doesn't appear until entering Template:Stage and its alts, or Template:Stage in Greed Mode.
10	Pure Magenta	Periodically shoots short-ranged blood shots, similar to Gushers.	Nothing	Common
11	Mostly Pure Violet	Pulls Isaac and his shots towards itself, like a Gaping Maw.	Random trinket	Around 10x rarer than common champions.	Doesn't appear until entering Template:Stage and its alts, or Template:Stage in Greed Mode.
12	Dark Red	Collapses into a flesh pile upon death and regenerates if not finished off (like a Globin).	Double Heart	Around 2x rarer than common champions.
13	Very Light Blue	Releases blood shots in 8 directions when killed.	1/2 heart	Common
Afterbirth
14	Camouflage	The enemy blends into the background and briefly becomes visible when damaged.	Rune	Around 4x rarer than common champions.
15	Pulsing Strong Lime Green	Splits into two copies of itself upon death.	2 normal versions of itself	Around 4x rarer than common champions.
16	Pulsing Dark Gray	Repels Isaac's shots when it pulses.	Nothing	Around 4x rarer than common champions.
17	Light White	Has 1-2 Eternal Flies circling it. Spawns another fly upon death.	Attack Fly	Around 4x rarer than common champions.
18	Small	Decreased health, increased speed and pitch of sound effects. 50% smaller both visually and collision-wise, making them more difficult to hit.	One Makes You Small pill at 1/5th of difficulty based drop rate.	Around 4x rarer than common champions.	Using the pill dropped will change all other pills matching its color into One Makes You Small pills.
19	Large	Increased health, slightly decreased speed and decreased pitch of sound effects. Visually 50% larger, though collision remains the same. Deals two full hearts of damage.	One Makes You Larger pill at 1/5th of difficulty based drop rate; can change other pills in the current rotation.	Around 4x rarer than common champions.	Using the pill dropped will change all other pills matching its color into One Makes You Larger pills.
Afterbirth+
20	Pulsing Vivid Red	All other enemies in the room regenerate health at the rate of 20 HP per second while this enemy is alive.	Heart	Around 10x rarer than common champions.	Doesn't appear until entering Template:Stage and its alts, or Template:Stage in Greed Mode.
21	Pulsating	Spawns an Attack Fly on hit. After each hit, there is a delay until the next hit results in another Attack Fly. A single Pulsating enemy can have up to 5 Attack Flies at once.	4-6 Blue Flies	Around 10x rarer than common champions.	Doesn't appear until entering Template:Stage and its alts, or Template:Stage in Greed Mode.
22	Crown	Increased health. All enemies in the room that are not champions will turn yellow while the crowned enemy is alive. The affected enemies will drop batteries like yellow champions upon dying, but otherwise have no extra health, speed or damage	2-3 random pickups	Around 10x rarer than common champions.	Doesn't appear until entering Template:Stage and its alts, or Template:Stage in Greed Mode.
23	Skull	Produces a The Necronomicon effect upon death. Deals two full hearts of damage.	The Necronomicon effect	Around 10x rarer than common champions.	Doesn't appear until entering Template:Stage and its alts, or Template:Stage in Greed Mode.

The chances for Champion monsters to appear are noted in the table below:

Modifiers	Normal mode	Hard mode	The Void
Base chance	5%	20%	75%
Champion Belt	20%	35%	75%
Purple Heart	10%	40%	100%
Purple Heart + Mom's Box	20%	80%	100%
Champion Belt + Purple Heart	40%	70%	100%
Champion Belt + Purple Heart + Mom's Box	80%	100%	100%

• Champion Belt adds 15% to the base champion chance. This has no effect in The Void.
• Purple Heart doubles the champion chance, and stacks with Champion's Belt.
  • Mom's Box changes Purple Heart to quadruple the chances instead of doubling.

• 

  Concept art for the champion versions of the Nest.

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!)

Base Monster	Replacement	Chance	Notes
Rebirth
		10%
		1%
		6%
		6%
		5%
		5%
		5%
		1%
		10%
		1%
		10%
		6%
		1%
		10%
		10%
		5%
		1%
		6%
		10%
		6%
		6%
		1%
		6%
		1%
		6%
		6%
Afterbirth
		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
		50%	Exclusive to Flooded Caves
		50%	Exclusive to Flooded Caves
		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+
		10%
		20%
		20%
		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

The Binding of Isaac: Rebirth
Achievements Challenges Completion Marks Items Trinkets Characters Chapters Rooms Transformations Attributes Bosses Monsters Pickups Modes Curses Objects Seeds Effects Endings
Collection Item Pools Version History Modding Music