Mystery Egg

Effect

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.

Notes

The usefulness of the enemy depends on how many rooms have been cleared without getting hurt.
- For Greed Mode and Greedier Mode, the usefulness of the enemy is based on waves cleared rather than rooms.
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, (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 |

Synergies

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.

Interactions

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

Bugs

| (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. |