Boss Room

Boss Rooms contain one of the many bosses, with victory granting Isaac an item from the Boss pool, hearts (depending on difficulty), and a trap door leading to the next level.

Notes

• Double Trouble Boss Rooms contain 2 bosses of the same type from the previous chapter. Defeating them only gives one item. Double Trouble Boss Rooms only appear from chapter 2 onward.
  • Double Trouble Boss Rooms can now contain 2 bosses of different types. Additionally, they can appear as early as chapter 1.
• If the floor is affected by Curse of the Labyrinth, 2 separate Boss Rooms will appear in series. The trapdoor to the next floor will only appear after defeating the second boss.
• When a boss is defeated, an entrance to a Devil Room or Angel Room can appear.
  • A Devil Room door can't appear on the first floor, unless Joker is used. A Devil Room door can also appear in a boss room on the first floor if the floor is spawned with the Curse of the Labyrinth, in which the Devil Room door will appear after defeating the second boss.
  • Upon defeating Mom's Heart, a Devil Room containing a trapdoor or an Angel Room containing a beam of light may appear. This allows Isaac to visit Sheol or Cathedral respectively even if It Lives has not yet been unlocked. If one of these paths is taken instead of touching the large chest, the next Mom's Heart ending will not play but will be unlocked and it will count as a victory against Mom's Heart.
    • Devil Rooms and Angel Rooms no longer contain a trapdoor or a beam after defeating It Lives. They instead have their normal contents.
• Mr. Fred, Tuff Twins, Great Gideon, The Shell, and Mega Satan are always fought in a double-sized room.
  • Hush is always fought in a 2x2 room and Ultra Greed is fought in a double-sized one (2x1).
  • Delirium is fought in a 2x2 room.
  • Mother is a fought in a regular room in her first phase, which expands to a 2x1 room for her second.
• Before the boss has been defeated, the eyes of the skull above the boss room's door are flashing.

The Binding of Isaac: Rebirth
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