Isaac (Boss)

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File:Boss Isaac (Boss) name.png
Boss versus screen image
In-game appearance
Stage cathedral.png
Stage the void.png
Final Boss Chest (The Chest)
Disambig.png This article is about the boss. For the character, see Isaac.

Isaac is the boss of 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. It is also accessable by using a teleport item prior to entering the boss room on the final floor.

Behavior[edit | edit source]

Note: During all three of Isaac's phases, he will always shoot multiple tears in the player's direction at fixed intervals. These tears can be double tears or even triple tears.

Isaac will not begin attacking the player until he takes damage.

Phase 1

  • Shoots 12 lines of tears in every direction.
  • Shoots 8 groups of tears in a spinning pattern.
  • Shoots 8 groups of spinning tears together with 8 lines of tears in every direction.

Phase 2

  • 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 Cricket's BodyCricket's Body Icon.pngGrants -1 Tear Delay and reduces Range. When tears hit an object or deplete their range, they spawn 4 smaller tears, whose Range and Damage scale with Isaac's..
  • Shoots 8 tears in all directions.
  • Summons Angelic Babies in pairs.
    • Added in Afterbirth † They'll always spawn in the bottom center of the room.
  • Summons two beams of light, similar to the beams summoned by Crack the Sky Crack the SkyCrack the Sky Icon.png4 roomsSummons multiple beams of light in random locations around the room, dealing a large amount of damage to any enemy that touches them..

Phase 3

  • Angelic Babies cease spawning.
  • Isaac grows angel wings and gains the ability to teleport.
  • Fires 12 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.
  • Teleports off screen and summons beams of light to cover the screen, starting from one of the top corners to the opposite bottom corner.

Gallery[edit | edit source]

Unlockable Items[edit | edit source]

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.

Strategy[edit | edit source]

Since Isaac does not attack the player until he is damaged, an effective strategy can be to use Remote Detonator after placing down many bombs. The bombs will not explode until remote detonator is used, dealing massive damage to Isaac. However, this requires the player to have a decent number of bombs (or a Gold bomb). Having bomb synergy items (i.e. Mr. Mega, Bob's Curse, etc.) improves this strategy further.

During the second phase of the fight, attempt to damage Isaac enough to push him into his third phase as quickly as possible. The beams of lights spawned during this phase are random; the more time spent on this phase, the greater the likelihood of getting hit by them.

In Isaac's third phase, the beams of light he summons are hard to dodge, but they do have areas where damage can be greatly minimized. For example, if the beams of light start in the upper left corner, they will never hit the bottom left corner or the top right corner, but they can hit the bottom right corner. As a result, making it to a corner adjacent to where the beams begin is the optimal strategy to reduce the likelihood of taking damage from this attack, and going to the opposite corner is the next best thing as beams only sometimes hit that area. Barring these two strategies, running through the beams in the opposite direction they are coming from (if timed correctly) does not hurt Isaac.

Trivia[edit | edit source]

  • 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. Oddly it's noted that Isaac's expression as the fight goes on goes from a somber, scared tone to him smiling in his third phase. This supports the theory that Isaac has made peace with himself and realized what he must do, as seen through the multiple endings of the game.
  • During his first phase, Isaac makes the same crying sound as Mulligans. This also applies to ???.

References[edit | edit source]

Bosses Boss Monstro.png
Chapter 1
Stage basement.png
Stage cellar.png
Stage burning basement.png
Blighted OvumDingleThe Duke of FliesFamineFistulaGeminiGurglingsThe HauntLarry Jr.MonstroPinStevenWidow
Added in Afterbirth DangleLittle HornRag ManTurdlings
Chapter 2
Stage caves.png
Stage catacombs.png
Stage flooded caves.png
Carrion QueenC.H.A.D.ChubDark OneGurdyGurdy Jr.The HollowThe HuskMega FattyMega MawPeepPestilencePolycephalusThe Wretched
Added in Afterbirth The ForsakenThe FrailThe Stain
Added in Afterbirth † Big HornRag Mega
Chapter 3
Stage depths.png
Stage necropolis.png
Stage dank depths.png
The AdversaryThe BloatThe CageThe GateGishLokiMask Of InfamyMonstro IIWarMom
Added in Afterbirth Brownie
Added in Afterbirth † Sisters Vis
Chapter 4
Stage womb.png
Stage utero.png
Stage scarred womb.png
BlastocystThe BloatConquestDaddy Long LegsDeathLokiiMama GurdyMr. FredScolexTeratomaTriachnidMom's HeartIt Lives
Added in Afterbirth † Sisters VisThe Matriarch
Added in Afterbirth Blue Womb
Added in Afterbirth Hush
Chapter 5
Stage sheol.png
Stage cathedral.png
Chapter 6
Stage dark room.png
Stage chest.png
???The LambMega Satan
Added in Afterbirth Greed Mode
Ultra Greed
Added in Afterbirth Ultra Greed
Added in Afterbirth † Ultra Greedier
Added in Afterbirth † The Void
Stage the void.png
Added in Afterbirth † Delirium
Chapters 1-4 The FallenThe Headless Horseman

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