Binding of Isaac: Rebirth Wiki
Binding of Isaac: Rebirth Wiki
Ultra   Hard
Character Isaac appearance.png
Full red heartFull red heartFull red heart
Table dividing line 1.png
Challenge Number
Starting Items
15►Key Piece 1 Key Piece 1
15►Key Piece 2 Key Piece 2
Available Rooms
Item Pool Treasure Room.png: yes          Item Pool Shop.png: yes
Boss Mega Satan.png
Unlock Method

Ultra Hard Removed in Repentance Defeat ??? or The Lamb. Possession of 15►The Polaroid The Polaroid/15►The Negative The Negative is required, barring getting to Dark Room Dark Room through a Sacrifice Room.
Added in Repentance Defeat Mega Satan

Added in Afterbirth †

Ultra Hard is Challenge #34. Isaac begins with both halves of the key for the Mega Satan battle and has to beat Mega Satan through the Dark Room.


This challenge, like the name suggests, is extremely difficult:

  • All enemies with champion forms, including bosses, will be champions.
    • Champions will not drop any collectibles.
  • The player suffers from the following curses each floor: Curse of the Labyrinth, Curse of the Lost, Curse of the Maze and Curse of the Blind.
    • These curses cannot be stopped through the usual methods of removing curses, such as the Rune of Dagaz Rune of Dagaz.
    • In addition to the four curses, the player may additionally suffer from either Curse of the Unknown or Curse of Darkness, which can be removed through usual means.
  • There are no hearts to be found in this run - red, soul, black, eternal, bone, golden, blended and rotten hearts.
    • Hearts can still be obtained through passive items that grant them upon collection, such as 15►Super Bandage Super Bandage or 15►Latch Key Latch Key.
    • Items and cards that normally drop hearts such as V - The Hierophant V - The Hierophant tarot card will not drop any hearts. Using an Ace of Hearts Ace of Hearts card will consume all pickups in the room, and not drop any hearts.
    • However, items that add hearts directly to the player's count (such as Balls of Steel or the 15►Satanic Bible Satanic Bible) will work.
  • Every boss fight that can be, will be double trouble.
    • Since the Basement can't have double trouble bosses, these don't start until Caves Caves.
  • Only 15►The Negative The Negative drops after killing Mom.
    • This forces the player to progress through Sheol Sheol and the Dark Room Dark Room to fight Mega Satan.
      • Even though the option to proceed upward through the Cathedral Cathedral is presented, the run will end after defeating Isaac and touching the chest will not give the player credit for completing the challenge.
        • The player can also beat the challenge by defeating Delirium.
          • Some players report no victory trophy spawning after defeating Delirium, under unknown conditions. It may not be safe to attempt this route.
    • Because the player cannot progress through Chest Chest, they are unable to take advantage of the 4 items at the start of the Chest floor. Added in Repentance However, the four Devil Deal chests at the start of the Dark Room may be useful if Isaac is willing to gamble his health for them.
  • If the player manages to defeat Hush, the entrances to the Cathedral Cathedral, Sheol Sheol, and The Void The Void appear.


  • Attempt to find valuable items from the two items rooms that appear in the Basement.
  • The 15►D10 D10 can be surprisingly helpful; most of the time, it will reroll enemies into non-champion forms, and as the D10 can never reroll enemies into portals, it makes managing rooms with portals much easier.
    • Added in Repentance The D10 rerolls champion enemies into new champion enemies. Additionally, portals no longer spawn outside of The Void The Void.
  • The 15►Glowing Hour Glass Glowing Hour Glass will allow the player to retry difficult rooms, avoid detrimental items, and peek at pills without the risk of harmful effects.
  • Trinkets that drops hearts as pickups such as Bloody Penny Bloody Penny or Monkey Paw Monkey Paw are useless in this challenge. However, those that directly heal such as Isaac's Fork Isaac's Fork or Stem Cell Stem Cell will still function.
  • 15►PHD PHD is very valuable, as it reveals all pills, replaces detrimental pill effects with positive ones, and heals two red hearts upon pickup.
  • Hematemesis is a major problem in this challenge as it drains all your red hearts and does not give them back.
  • Removed in RepentanceItems that reroll the player such as the 15►D4 D4 and the 15►D100 D100 can be used to amass health very quickly, as hearts generated from items are not removed if the items that granted them are rerolled.
    • Added in RepentanceItems lost from the 15►D4 D4 and the 15►D100 D100 now remove associated hearts.
  • The 15►Clicker Clicker can potentially transform Isaac into Keeper Keeper, allowing him to heal with coins. That said, using it will remove your most recently collected item, so it shouldn't be used if it would remove a powerful item or 15►Key Piece 2 Key Piece 2.
  • Look for Libraries and Bedrooms. Both of these rooms contain resources that can replenish the player's health.
  • Rainbow Poops can be destroyed to fully heal the player.
  • Bombing Tinted Rocks is much less beneficial for the player, as soul hearts will not drop from them.
    • Tinted Rocks can still contain 15►The Small Rock The Small Rock, however, so if the player has a surplus of bombs or another way to destroy rocks, there is no reason to not destroy them.
  • Deals found in Devil Rooms are generally not worth taking. It may be preferable to pursue Angel Rooms instead, as the player already has both key pieces, which greatly increases their chances of spawning. Due to no Soul hearts or Black hearts being able to spawn naturally, taking damage and lowering the chance for a Devil / Angel room is very common. Make sure to find items that give these hearts such as Book of Revelations or Satanic Bible.
    • One-heart deals are almost never beneficial — many one-heart deals do not pay for themselves, whether that be in health or other effects. Avoid taking one-heart deals unless you are confident that they are worth their cost.
    • Two-heart deals are very powerful, such as 15►The Pact The Pact and 15►Brimstone Brimstone. Be wary that 15►Abaddon Abaddon can remove the player's red hearts, making items such as 15►Pyromaniac Pyromaniac, 15►Yum Heart Yum Heart and 15►Placenta Placenta useless until the player regains red hearts.
      • Judas' Tongue Judas' Tongue will hide two-heart deals due to Curse of the Blind. It is therefore a bad idea to hold Judas' Tongue if the player desires to extract powerful items from a deal.
    • If Red Chests spawn in the Devil Room, be wary of picking up any items that they may contain. The Red Chest item pool contains powerful items such as 15►Dead Cat Dead Cat but also contains potentially run-ruining items such as 15►Cursed Eye Cursed Eye and 15►Curse of the Tower Curse of the Tower.
  • Do not enter Curse Rooms and do not use Sacrifice Rooms.
    • Curse Rooms very rarely contain a worthwhile item, and as Curse of the Blind is in permanent effect, it is impossible to tell if an item in a Curse Room contains a good item, such as 15►Dead Cat Dead Cat, or a bad item, such as 15►Curse of the Tower Curse of the Tower.
    • Sacrifice Rooms do allow the player to potentially obtain a powerful Angel Room item; however, spending at least three full hearts for a chance at getting an item is almost always not worth it, especially as hearts do not naturally drop. Additionally, there is no reason to fight the angels, as the player already has both key pieces, and there is no reason to teleport early to the Dark Room and skip multiple Treasure Rooms, as the player is forced to take 15►The Negative The Negative anyways.
  • Removed in RepentanceThe Colorful Baby, which can be utilized in co-op mode, makes the Ultra Hard challenge trivial, as its healing effect can be used infinitely.



  • Despite being the "Ultra Hard" challenge, this challenge is actually played in Normal Mode. Although it is not as noticeable in Afterbirth, in Repentance, it is far easier to notice due to the lowered shot speed of many enemies.

MainPageChallenges.png Challenges MainPageChallenges.png

1. Pitch Black 2. High Brow 3. Head Trauma 4. Darkness Falls 5. The Tank 6. Solar System 7. Suicide King
8. Cat Got Your Tongue 9. Demo Man 10. Cursed! 11. Glass Cannon 12. When Life Gives You Lemons 13. Beans! 14. It's in the Cards
15. Slow Roll 16. Computer Savvy 17. Waka Waka 18. The Host 19. The Family Man 20. Purist
21. XXXXXXXXL 22. SPEED! 23. Blue Bomber 24. PAY TO PLAY 25. Have a Heart 26. I RULE! 27. BRAINS!
28. PRIDE DAY! 29. Onan's Streak 30. The Guardian
Afterbirth †
31. Backasswards 32. Aprils Fool 33. Pokey Mans 34. Ultra Hard 35. Pong
36. Scat Man 37. Bloody Mary 38. Baptism by Fire 39. Isaac's Awakening 40. Seeing Double 41. Pica Run 42. Hot Potato
43. Cantripped! 44. Red Redemption 45. DELETE THIS
The Binding of Isaac: Rebirth The Binding of Isaac: Rebirth The Binding of Isaac: Rebirth
Achievements Achievements Attributes Attributes Bosses Bosses TarotCard.png Cards and Runes Challenges Challenges Chapters Chapters
Characters Characters MainPageBabies.png Co-op Items Items Item pools Item pools Monsters Monsters Objects Objects
Pickups Pickups Pills Pills Rooms Rooms Seeds Seeds Transformations Transformations Trinkets Trinkets