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 (Womb/Utero/Scarred Womb), 3 waves of bosses will be spawned, typically from Chapters 1 or 2.

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:

Floor	Wave 1	Wave 2	Wave 3
Basement	3 Hoppers	3 Horfs	2 Clotties
Basement	5 Attack Flies	5 Pooters	4 Gapers
Cellar	3 Fatties	3 Round Worms	5 Dips
Cellar	3 Gapers	3 Horfs	3 Fatties
Caves	5 Chargers	4 Globins	4 Maws
Caves	5 Spitties	3 Hives	3 Hosts
Catacombs	2 Bonies	2 Tumors	3 Wall Creeps
Catacombs	4 Round Worms	3 Nightcrawlers	1 Grub
Depths	3 Vis	4 Leapers	4 Globins
Depths	4 Babies	5 Hoppers	4 Knights
Necropolis	4 Knights	3 Mom's Hands	3 Fat Sacks
Necropolis	4 Bonies	2 Squirts	3 Nulls
Womb Utero	3 Larry Jrs	Chub and 3 Chargers	2 Monstros
Womb Utero	Fistula	Loki	Chub
Cathedral Sheol	3 Larry Jrs	Chub and 3 Chargers	2 Monstros
Cathedral Sheol	Fistula	Loki	Chub

Waves (Sorted By Difficulty; Basement, Cellar, and Burning Basement Unused)

Floor	Easy	Normal	Hard	Hardest
Basement	3 Hoppers / 5 Attack Flies / 4 Dips	3 Horfs / 5 Pooters / 2 3-Segment Army Flies	2 Clotties / 4 Frowning Gapers / 1 Squirt and 2 Dips	3 Level 2 Flies and 2 Full Flies / 3 Suckers / 4 Cyclopias / 3 Ministros
Cellar	3 Level 2 Spiders / 5 Spiders / 3 Sacks	4 Trites / 3 Small Crazy Long Legs / 3 Wall Creeps	2 Nests / 2 Crazy Long Legs / 3 Small Baby Long Legs	2 Baby Long Legs / 2 Big Spiders and 2 Spiders / 2 Blind Creeps / 2 Migraines
Burning Basement	2 Flaming Hoppers	5 Dart Flies / 2 Pairs of 5 Swarm Flies / 2 Pairs of 4 Swarm Spiders	3 Flaming Fatties / 4 Suckers / 2 Grilled Clotties	4 Flaming Hoppers / 4 Crispies
Downpour	2 Blurbs / 5 Small Leeches / 4 Striders	4 Frowning Gapers and 1 Wraith / 2 Preys / 3 Sub Horfs	5 Willos and 2 Striders / 2 Bubbles and 2 Striders / 3 Bloaties	4 Sub Horfs and 2 Blurbs / 2 Mullighouls
Dross	5 Drips / 5 Small Leeches / 2 Dump Heads	3 Cloggies / 2 Fartigans and 4 Gas Clouds / 4 Big Corns	4 Blurbs / 2 Bubbles and 2 Sub Horfs / 3 Dumps	2 Cloggies and 1 Splurt / 2 Fartigans and 2 Poot Mines
Caves	5 Conjoined Spitties / 4 Boils / 6 Maggots	3 Hives / 3 Globins / 4 Chargers	3 Hosts / 3 Maws / 2 Conjoined Fatties	4 Pale Fatties/ 2 Tumors / 4 Red Boom Flies
Catacombs	5 Round Worms / 4 Wall Creeps / 4 Splashers	3 Night Crawlers / 2 2-Segment Buttlickers and 1 3-Segment Buttlickers / 3 Boom Flies	1 3-Segment Grub / 3 One Tooths / 3 Psychic Horfs	2 Mobile Hosts / 4 Chubbers / 4 Gurgles
Flooded Caves	4 Conjoined Spitties / 3 Drowned Boom Flies	2 Drowned Hives / 3 Globins / 3 Night Crawlers	4 Maws / 2 Squirts / 2 Drowned Boom Flies and 2 Dukies	4 Blubbers and 2 Conjoined Fatties / 5 Drowned Chargers / 3 Tube Worms
Mines	4 Soy Creeps / 4 Inks / 3 Fly Bombs	2 Quakeys and 2 Rock Spiders / 2 Inks and 2 Soy Creeps / 2 Hard Hosts	2 Dannies / 2 Gyros / 2 Gyros and 1 Bouncer / 2 Hardies	2 Blasters / 4 Facelesses / 4 Moles
Ashpit	3 Bonies / 6 Rock Spiders / 3 Clickity Clacks	3 Bone Flies / 3 Flesh Maidens / 2 [[Horf#Necro\|Necros	2 Hardies / 3 Big Bonies / 3 Carrion Princesses / 4 Dusts	3 Pasties / 2 Blasters and 2 Fly Bombs / 4 Bonies and 3 Dusty Death's Heads / 3 Crackles
Depths	3 Vises / 4 Babies / 4 Brains	4 Leapers / 5 Rotties / 3 Lil' Haunts	4 Knights / 3 Fat Sacks / 3 Needles	3 Mr. Maws / 3 Wizoobs / 3 Mom's Hands / 2 Mr. Red Maws
Necropolis	3 Bonies / 3 Gurgles / 2 Lil' Haunts	2 Swarmers and 4 Pooters / 3 Double Vises / 3 Rage Creeps	2 Mask + Heart Pairs / 4 Keepers / 3 Psychic Maws / 3 Eggies	3 Fat Sacks / 3 Wizoobs / 3 Hangers / 1 Dingas
Dank Depths	4 Clots / 2 Dank Squirts / 2 Sticky Leapers	6 Dank Death's Heads / 1 Mega Clotty / 4 Slogs / 6 Inks	3 Black Bonies and 2 Death's Heads / 4 Black Bonies / 3 Dank Chargers / 2 Tar Boys and 1 Dank Squirt	1 Mom's Dead Hand and 1 Dank Globin / 4 Dank Globins / 2 3-Segment Butt Slickers / 5 Sticky Leapers
Mausoleum	3 Bonies / 2 Psychic Maws / 4 Soul Suckers	2 Loose Knights / 2 Whippers / 4 Candlers / 1 Cursed Globin	2 Snappers / 2 Vis Versas / 2 Vis Fatties /2 Vis Versas	2 Lil Portals/1 Bony and 2 Cultists / 2 Bishops and 2 Baby Begottens / 2 Revenants
Gehenna	3 Bonies / 4 Soul Suckers \| 2 Begottens / 2 Poofers	2 Whippers / 2 Baby Begottens / 1 Cursed Globin / 2 Snappers	2 Maze Roamers / 2 Vis Versas / 2 Vis Fatties / 2 Black Knights	3 Blood Cultists / 2 Mask II + 1/2 Hearts Pairs / 8 Goats / 3 Black Goats
Womb	3 3-Segment Larry Jr.s / 2 MemBrains / 3 Freds	4 Leeches / 3 Swingers / 2 Mega Clotties	1 Chub / 2 Monstros / 1 Fistula	2 Geminis / 2 Pins / 2 Polycephaluses
Utero	3 3-Segment The Hollows / 2 Mama Guts / 4 Hearts	2 Oobs / 3 Gurglings / 4 Para-Bites/ 2 Planetoids	1 C.H.A.D/ 3 Mask + Heart Pairs / 2 Widows / 4 Red Ghosts/2 Floating Hosts	2 Blighted Ovums / 1 Gluttony and 1 Super Gluttony / 1 Blastocyst (Small) and 4 Embryos / 4 Poison Minds/2 Peeping Fatties
Scarred Womb	1 Mama Guts and 4 Scarred Guts / 2 Red Hosts and 2 [[[Brain]]s \| 3 Fistuloids	4 Scarred Double Vises / 4 Scarred Para-Bites	4 Meatballs / 3 Flesh Mobile Hosts / 2 Monstros / 2 Eyes and 4 Nerve Endings / 2 Lepers (Stage 2) and 2 Lepers (Stage 4)
Corpse	20 Small Maggots / 2 Sloths / 2 Level 2 Chargers and 4 Chargers / 4 Pustules	3 Wrinkly Babies / 3 Sick Boom Flies / 2 Level 2 Horfs / 3 Twitchies	3 Cysts/ 1 Cohort / 2 Mama Flies and 4 Pustules / 2 Level 2 Gapers	1 Chub, 2 Chargers, and 5 Small Maggots / 1 Adult Leech and 2 Leeches / 2 Cysts and 1 Dead Meat/4 Level 2 Chargers
Cathedral	3 Holy Leeches / 3 Angelic Babies / 4 Bonies and 2 Death's Heads	5 Wizoobs / 7 Pale Fatties / 4 Hangers / 3 Candlers	2 Wraths / 2 Psy Tumors / 1 Daddy Long Legs / 2 Bishops and 1 Angelic Baby / 2 Holy Mulligans	1 Conquest / 1 Headless Horsemen Heads / 2 Greeds / 2 Holy Bonies
Sheol	4 Kamikaze Leeches / 3 Begottens / 3 Black Globins / 3 Imps	3 Selfless Knights / 2 Black Maws / 4 Black Globin's Heads / 3 Whippers	4 Nulls / 2 Bloodshot Eyes / 2 Camilio Jr.s / 2 Snappers / 2 Bloodshot Eyes and 1 Soul Sucker	2 Greeds / 1 Death / 2 Dark Ones / 1 The Pile

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:

Boss Waves

Floor	Wave 1	Wave 2
Basement	Monstro	Larry Jr.
Cellar	Pin	Gurglings
Cellar	Dingle	Gemini
Caves	Chub	Peep
Catacombs	Mega Fatty	Mega Maw
Catacombs	Fistula	The Haunt
Depths	Loki	Monstro II
Necropolis	Mega Maw	The Husk
Necropolis	Dark One	Loki

Boss Waves (Sorted By Difficulty)

Floor	Easy	Normal	Hard
Basement	Monstro / Gemini	3 3-Segment Larry Jr. / The Duke of Flies	Gurglings / Dingle
Cellar	Pin / The Duke of Flies	Widow/Blighted Ovum	The Haunt / Little Horn / Baby Plum
Burning Basement	Dangle	Turdlings / Little Horn	Rag Man
Downpour	The Haunt	The Rainmaker	Lil Blub / Min-Min
Dross	Dingle	Lil Blub	5-Segment Turdlet/Clog
Caves	Chub / Fistula	Peep / Gurdy Jr. / Pin and 2 Needles	Polycephalus / Mega Maw
Catacombs	The Husk / 2 4-Segment The Hollows	The Wretched and 2 Trites / Gurdy Jr. / The Stain	Dark One / Carrion Queen
Flooded Caves	The Forsaken / Gurdy Jr.	The Stain/Rag Mega	The Frail / Big Horn
Mines	2 Wraths	4-Segment Larry Jr., 5-Segment Tuff Twin, and 1 Bomb Grimace	Reap Creep
Ashpit	Super Wrath	The Pile	Singe and 4 Singe's Ball / 5-Segment The Shell and 1 Bomb Grimace
Depths	Loki / Gurdy	Monstro II / 2 Little Horns	The Bloat/The Gate
Necropolis	Loki	The Adversary/The Pile	The Cage/Mask of Infamy
Dank Depths	Gish / Monstro II	2 Little Horns/2 Rag Men	Brownie/Sisters Vis
Mausoleum	Rag Mega	The Heretic	The Siren
Gehenna	Sisters Vis	The Visage	The Horny Boys
Womb	Blastocyst / Lokii	The Stain / 3 Gurglings	The Bloat/The Cage
Utero	Blastocyst / Lokii	Teratoma / Daddy Long Legs	The Bloat/2 Gurdy Jr.s
Scarred Womb	Blastocyst / Polycephalus / Lokii	Fistula/ Gurdy Jr. + 1 Gurgling	The Matriarch / The Bloat / Mama Gurdy
Corpse	2 Super Sloths / 2 Super Gluttonies	Chimera / 2 Chubs	The Scourge

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.

ID	Weight	Notes
0-2	1.0	This room appears three times in the room pool, making it three times more likely to appear than normal.
3-4	1.0	This room appears twice in the room pool, making it twice as likely to appear than normal.
5	0.5	The item will be from the Treasure Room pool.
6	1.0
7	0.75
8	0.5
9	0.5
10	0.5
11	1.0
12	1.0

Notes

Temporary Tattoo will cause an additional chest to spawn after a normal Challenge Room is completed as well as cause an additional item from the Boss item pool to spawn after completing a Boss Challenge Room.
The waves appear in random orders rather than the orders listed above.
If Isaac has some way to teleport out of the room, the contents of the Challenge Room can be taken without fighting the enemies.
- If a trigger to start a challenge room is left in the room after teleporting out (such as a chest or active item) or an item is spawned in the room and collected (such as rewards from Beggars or Blood Donation Machines), the challenge room will start over when it is picked up/opened.
If a Secret Room is next to a Challenge Room, it can be entered by using a bomb in the Secret Room on the wall separating the two rooms. However, the entrance to the Secret Room from the Challenge Room closes itself, meaning Isaac cannot escape through the Secret Room entrance.
- If Isaac bombs into either variation of Challenge Room through a Secret Room and leaves, the bombed entrance will close until and must be bombed open again.
If Spiders spawn from a Red Chest before or during a wave, the Spiders have to be killed in order for the waves to start/continue.
- If Spiders spawn from a Red Chest after the challenge room is cleared, Isaac can leave the room without fighting them.
Because of the health requirements, both types of Challenge Room will always be open for The Lost and ???.
- As Boss Challenge Rooms now take soul hearts into account, Soul Heart characters are now also forced to be at one heart before being allowed access.
Doors to challenge rooms can be opened regardless of health with Dad's Key or Mr. ME!

Bugs

Bug!	If the game crashes or you close it before you finish the challenge room it will crash every time you try to continue that run.

Bug!	If Isaac encounters Greed or Super Greed in a Secret Room next to a boss challenge room, the path to the boss challenge room is boarded up from the mini-boss fight. Defeating Greed or Super Greed does not remove the boards, despite the room no longer being active.