Challenge Room

Challenge Rooms are special rooms that allow Isaac to fight enemies for extra rewards. They will only spawn on a floor if, upon entering the floor, Isaac's total health is greater than or equal to his number of heart containers. There are two kinds of challenge rooms: Normal Challenge Rooms, which appear on the first floor of a chapter or on XL floors, and Boss Challenge Rooms, which appear on the second floor of a chapter.

Normal Challenge Room


Normal Challenge Rooms can only be entered if Isaac's total health (Red, Black, and Soul Hearts) is greater than or equal to his number of heart containers. Picking up its contents will cause three waves of enemies to spawn. While in chapter 4 (/), 3 waves of bosses will be spawned (usually bosses from /).

Each wave cleared will charge Isaac's active item by 1.

Waves
The enemies that spawn depend on the current chapter, and each chapter has two different possible sets of enemies:

Boss Challenge Room


Boss Challenge Rooms can only be entered if Isaac has one or fewer hearts of health. Picking up its contents will cause two waves of bosses to spawn. Starting on Chapter 4, they use the same waves of bosses as Normal Challenge Rooms.

Each wave cleared will charge Isaac's active item by 1.

The Boss Challenge Room door only counts Red Hearts in determining whether Isaac is allowed to enter. Soul Hearts are ignored. Boss Challenge Rooms require one or fewer hearts total to enter, counting Soul Hearts. Boss Challenge Rooms will always contain an item from the Boss item pool.

The bosses that spawn depend on the current chapter. Alternate floors have two possible sets of bosses that could spawn:

Layouts
The following room maps were made using Basement Renovator for cleaner viewing; note that both normal and boss challenge rooms use the same layouts.