Isaac (Boss)
Boss Isaac (Boss)
Found In
Dropped Items
Final Boss Chest (The Chest)
Unlocked By
Defeating Mom's Heart

Isaac is the boss of The Cathedral which can be accessed by either killing Mom's Heart 11 times and proceeding to kill It Lives, or entering an Angel Room after killing Mom's Heart and walking into the beam of light that appears.

Attacks Edit

Note: During all three of Isaac's phases, he will always shoot multiple tears in the player's direction at fixed intervals.

First Phase

  • Fires multiple shots in the player's direction.
  • Shoots 8 tears in every direction.

Second Phase

  • Fires multiple shots in the player's direction.
  • Shoots 8 tears in every direction
  • Shoots 4 tears in the cardinal or diagonal directions, which will split into four short-ranged tears after a short time, similar to Cricket's Body.
  • Summons Angelic Babies in pairs.
  • Summons beams of light, two at a time.

Third Phase

  • Fires multiple shots in the player's direction.
  • Angel Babies cease spawning.
  • Isaac grows angel wings and gains the ability to teleport.
  • Fires fast lines of tears between each teleport.
  • Isaac will block the player by flying in front of them if they attempt to traverse behind or to the left/right of Isaac.
  • Summons beams of light to cover the screen, starting from one of the top corners to the opposite bottom corner. The beams of light sometimes hit the bottom corners of the room.

Unlockable Items Edit

The following items can be unlocked by beating Isaac with the corresponding character:

In addition, beating Isaac with a particular character for the first time will unlock the Cross Completion Mark on that character's post-it note.


  • The music that plays during this boss fight is titled Infanticide [1]. The term infanticide refers to the act of killing an infant or newborn.
  • Isaac, along with ???, are the only bosses who do not "die" upon losing all their health. Instead of exploding into a pile of gore, Isaac teleports away and the battle ends.





Bosses Boss Monstro
Basement MonstroGeminiDingleLarry Jr.The Duke of FliesGurglingsFistulaStevenFamine
Cellar Gurdy Jr.PinWidowBlighted OvumThe HauntDingleLarry Jr.The Duke of FliesGurglingsFistulaFamine
The Caves ChubGurdyGurdy Jr.Mega MawMega FattyDark OneC.H.A.D.Pestilence
Catacombs The HollowThe HuskPeepPolycephalusThe Carrion QueenThe WretchedDark OnePestilence
The Depths The CageMonstro IIThe AdversaryThe GateLokiGishWarMom
Necropolis The BloatThe Carrion QueenMask of InfamyThe WretchedThe GateLokiWarMom
The Womb Mr. FredScolexTeratomaMama GurdyThe BloatLokiiDeathConquestMom's HeartIt Lives
Utero BlastocystDaddy Long LegsTeratomaMama GurdyThe BloatLokiiTriachnidDeathConquestMom's HeartIt Lives
Sheol The FallenSatan
Dark Room The LambMega Satan
Cathedral Isaac
The Chest ???Mega Satan
Devil Room Krampus
Angel Room Angel
Levels 1-5/7 The FallenThe Headless Horseman
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