Hard mode

Hard mode changes the gameplay compared to Normal in some ways to make it more difficult. When playing in Hard mode, a small red pentagram () appears on the HUD, below the pickups.

Differences

• 2-3 more rooms generate each floor.
• Certain "easy" room layouts cannot generate, making difficult rooms more common.
• Enemies have a base 20% chance to become Champions instead of only 5%; additionally, they only award pickups 33% of the time.
• Hearts are 66% less likely to drop after completing a room.
• Only champion bosses will drop hearts; normal bosses will not.
• Floors are more likely to have curses.
• Floors are more likely to be replaced by their alternate versions (e.g. Necropolis or Dank Depths instead of The Depths).

Unlocks for Hard Mode

Character	Mom's Heart	All completion marks
Isaac
Magdalene
Cain
Judas
???
Eve
Samson
Azazel
Lazarus
Eden
The Lost
Lilith
Keeper
Apollyon
The Forgotten

Trivia

• Before update 1.03, the reduced drop-rate affected all pickups (not just Red Hearts).
• Godhead, Smelter, and Marrow are the only items that require playing Hard mode to unlock, with every other unlock being co-op babies.
• Godhead's unlock requirements were extended in the Afterbirth DLC (and further extended in the Afterbirth+ DLC) due to the addition of more completion marks, but it can still be unlocked in the base game using the same method.