Binding of Isaac: Rebirth Wiki

Added in Afterbirth †

Mystery Egg is an unlockable passive item added in The Binding of Isaac: Afterbirth † (Booster Pack #5).


  • Spawns an egg familiar, which cracks and turns into a random friendly enemy when Isaac is hurt.
    • The egg regenerates upon entering a different room.


  • The usefulness of the enemy depends on how many rooms have been cleared without getting hurt.
  • The list of available monsters is as follows:
Number of rooms / waves cleared Monsters
0 to 1 rooms cleared without taking damage Fly Fly, Attack Fly Attack Fly, Maggot Maggot, Spider Spider, Dip Dip, Embryo Embryo, Nerve Ending Nerve Ending
2 to 4 rooms cleared without taking damage Moter Moter, Pooter Pooter, Swarm Swarm, Level 2 Fly Level 2 Fly, Full Fly Full Fly, Horf Horf, Sucker Sucker, Dart Fly Dart Fly, Big Spider Big Spider, Guts Guts, Hopper Hopper, Gusher Gusher, Round Worm Round Worm, Mask + Heart Mask + Heart, Gush Gush
5 to 7 rooms cleared without taking damage Squirt Squirt, Ragling Ragling, Homunculus Homunculus, Level 2 Spider Level 2 Spider, Small Baby Long Legs Small Baby Long Legs, Wall Creep Wall Creep, Night Crawler Night Crawler, Ulcer Ulcer, Ministro Ministro, Mulligan Mulligan, Hive Hive, Nest Nest, Flaming Hopper Flaming Hopper, Gaper Gaper, Cyclopia Cyclopia, Skinny Skinny, Dople Dople, Globin Globin, Maw Maw, Psychic Horf Psychic Horf, Tumor Tumor, Fatty Fatty, Half Sack Half Sack, Clotty Clotty, Charger Charger, Brain Brain, Conjoined Spitty Conjoined Spitty, Buttlicker Buttlicker, Host Host, One Tooth One Tooth, Baby Baby, Dukie Dukie, Black Globin's Body Black Globin's Body, Black Globin's Head Black Globin's Head, Para-Bite Para-Bite
8 to 10 rooms cleared without taking damage Splasher Splasher, Boom Fly Boom Fly, Keeper Keeper, Fat Bat Fat Bat, Psy Tumor Psy Tumor, Imp Imp, Fred Fred, Cod Worm Cod Worm, Lump Lump, Swinger Swinger, Bony Bony, Black Globin's Body Black Globin's Body, Nulls Nulls, Begotten Begotten, Knight Knight, Bone Knight Bone Knight, Blubber Blubber, Conjoined Fatty Conjoined Fatty, Oob Oob, Leech Leech, MemBrain MemBrain, Wizoob Wizoob, Mr. Maw Mr. Maw, Flesh Death's Head Flesh Death's Head, Mushroom Mushroom, Blind Creep Blind Creep, The Thing The Thing, Blister Blister, Leaper Leaper, Hanger Hanger, Poison Mind Poison Mind, Fistuloid Fistuloid, Tar Boy Tar Boy
11 to 13 rooms cleared without taking damage Gurgle Gurgle, Walking Gut Walking Gut, Black Bony Black Bony, Black Maw Black Maw, Camillo Jr. Camillo Jr., Eye Eye, Roundy Roundy, Mom's Hand Mom's Hand, Mega Clotty Mega Clotty, Swarmer Swarmer, Fat Sack Fat Sack, Mobile Host Mobile Host
More than 13 rooms cleared without taking damage Red Ghost Red Ghost, Rage Creep Rage Creep, Vis Vis, Gurglings Gurglings, Dinga Dinga, Portal Portal


  • BFFS! BFFS!: The enemy spawned will be a champion variant and egg grows in size.
    • Even if the enemy spawned cannot be a champion under normal circumstances, they will become a champion.


  • Added in RepentanceEraser Eraser: Enemies erased by Eraser will never show up again, hindering Mystery Egg should it spawn said removed enemy.
  • Holy Mantle Holy Mantle: Losing the Mantle will not cause a friendly enemy to spawn.

In-game footage[]



Bug Bug! Removed in Repentance When using Extension Cord Extension Cord with Mystery Egg, after the egg turns into a friendly enemy, the electricity shoots out into a random corner of the room.
Bug Bug! When the egg turns into a friendly Heart ( Mask + Heart Mask + Heart) will sometimes act as the heart companion for a mask already in the room resulting in an unbeatable room.