Binding of Isaac: Rebirth Wiki

Added in Repentance

Mega Mush is an unlockable activated item added in The Binding of Isaac: Repentance.


  • Gigantifies Isaac for 30 seconds, persisting between rooms and floors. While Gigantic, Isaac gains the following effects;
    • Gains a 4x damage multiplier and ~+7 range, but a 2.5x tear delay multiplier.
    • Becomes invulnerable to damage.
    • Can destroy obstacles and objects and open doors by walking into them. This includes metal blocks.
      • Does not open challenge room doors or doors that require keys if you lack the keys.
    • Deals extremely heavy contact damage to enemies (80 per tick, or 1,600 per second).
  • This item belongs to the Fun Guy set. Collecting three items from this set will transform Isaac into a walking mushroom.


  • Using Mega Mush again while its effects are still active will add an additional 30 seconds to the current active time.
  • Isaac's physical size, i.e. collision circle or "hitbox" is roughly doubled in radius when Mega Mush is active. This is the only item that can make Isaac tangibly larger than his starting size, as normal size ups can't increase the collision area beyond the default.
  • Mega Mush will not negate the damage taken from the Mausoleum Mausoleum door. It's even possible to die this way, while the item is active.
  • Non-tear based attacks such as Brimstone Brimstone or Mom's Knife Mom's Knife are overridden by normal tears while Mega Mush is active.


  • 4.5 Volt 4.5 Volt: The contact damage dealt by Mega Mush will allow it to be recharged and used multiple times in the same room.
  • Car Battery Car Battery: Mega Mush's active time will be doubled to 60 seconds.


In-game Footage[]


  • Mega Mush is based off of the Mega Mushroom from the New Super Mario Bros. series, which would turn Mario giant, grant invulnerability, and allow him to defeat almost anything he touches.
  • Originally in Antibirth, the item didn't gain charges while active, and was unlocked by defeating Mother Mother (then known as The Witness) as every character on Hard Mode.
  • Entering the Big chest in Mega Mush form triggers the credits 0.5 seconds faster than normal (tested by entering the Big Chest going from the same position to the beginning of credits and timed with scripts)


PC 04AW R3W6 (Treasure room adjacent to spawn)

PC FQZF GB13 (Treasure room adjacent to spawn)


Bug Bug! Activating Mega Mush before entering the Knife Piece 2 area will keep the effect active inside the chase area but Isaac will have his normal sized, followed with a huge shadow and will continuously stomp the ground, breaking everything in his way, even pushing away Mother's Shadow.
Bug Bug! Using Mega Mush in combination with Suplex! Suplex! makes you grab enemies and move them around until you leave the room. Doing this on any of the Ultra Harbingers or The Beast The Beast will make the enemy disappear and render you unable to move at all.