| Floors of
| Base Health||2000|
|Unlocked By||Defeat It Lives|
|Items Dropped||Boss Chest|
Isaac will go through three stages depending on his health- the first at full health, the second at 3/4 health, and the third at 1/2 health. The stages are as follows:
1. Isaac will be lying on the ground, crying. His attacks are as follows:
- Isaac will shoot 12 lines of tears at Isaac (Player) in an asterisk pattern.
- Isaac will shoot waves of tears at Isaac (Player).
- Isaac will shoot 8 lines of tears in a spiral pattern.
- Isaac will shoot 8 lines of tears in a complex spiral pattern.
2. Isaac will be standing, looking up. His attacks are as follows:
- Isaac will keep all of the attacks from his first phase.
- Isaac will spawn two Angelic Babies.
- Isaac will shoot 4 splitting tears outwards.
- Isaac will summon a few beams of light that damage Isaac (Player).
3. Isaac will be flying, smiling and looking up. His attacks are in the order as follows:
- Isaac will fire 8 lines of tears in an asterisk pattern.
- Isaac teleports around and will fire waves of tears at Isaac (Player).
- After taking enough damage, Isaac will fly away, spawning a checker pattern of light beams across the room.
- The track title for the Isaac Boss fight is Infanticide.