Binding of Isaac: Rebirth Wiki

(in Afterbirth † and Repentance)

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

Effect[ | ]

  • Spawns an egg familiar, which cracks and turns into a random friendly monster when Isaac is hurt.
    • The egg regenerates upon entering a different room.
    • The usefulness of the enemy depends on how many consecutive rooms have been cleared without getting hurt.

Notes[ | ]

  • (in Repentance) Familiars that follow behind Isaac have a certain priority in how close their position is to him over other familiars, with Mystery Egg having the lowest priority at 6th and thus being farther from Isaac than familiars of different priorities.
  • Mystery Egg will activate when taking non-hostile damage (such as from a Blood Donation MachineBlood Donation Machine or Curse RoomCurse Room door).
  • 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 FlyFly, Attack FlyAttack Fly, MaggotMaggot, SpiderSpider, DipDip, EmbryoEmbryo, Nerve EndingNerve Ending
2 to 4 rooms cleared without taking damage MoterMoter, PooterPooter, SwarmSwarm, Level 2 FlyLevel 2 Fly, Full FlyFull Fly, HorfHorf, SuckerSucker, Dart FlyDart Fly, Big SpiderBig Spider, GutsGuts, HopperHopper, GusherGusher, Round WormRound Worm, Mask HeartMask + Heart, GushGush
5 to 7 rooms cleared without taking damage SquirtSquirt, RaglingRagling, HomunculusHomunculus, Level 2 SpiderLevel 2 Spider, Small Baby Long LegsSmall Baby Long Legs, Wall CreepWall Creep, Night CrawlerNight Crawler, UlcerUlcer, MinistroMinistro, MulliganMulligan, HiveHive, NestNest, Flaming HopperFlaming Hopper, GaperGaper, CyclopiaCyclopia, SkinnySkinny, DopleDople, GlobinGlobin, MawMaw, Psychic HorfPsychic Horf, TumorTumor, FattyFatty, Half SackHalf Sack, ClottyClotty, ChargerCharger, BrainBrain, Conjoined SpittyConjoined Spitty, ButtlickerButtlicker, HostHost, One ToothOne Tooth, BabyBaby, DukieDukie, Black Globin's BodyBlack Globin's Body, Black Globin's HeadBlack Globin's Head, Para-BitePara-Bite
8 to 10 rooms cleared without taking damage SplasherSplasher, Boom FlyBoom Fly, KeeperKeeper, Fat BatFat Bat, Psy TumorPsy Tumor, ImpImp, FredFred, Cod WormCod Worm, LumpLump, SwingerSwinger, BonyBony, Black Globin's BodyBlack Globin's Body, NullsNulls, BegottenBegotten, KnightKnight, Bone KnightBone Knight, BlubberBlubber, Conjoined FattyConjoined Fatty, OobOob, LeechLeech, MemBrainMemBrain, WizoobWizoob, Mr. MawMr. Maw, Flesh Death's HeadFlesh Death's Head, Mushroom (Enemy)Mushroom, Blind CreepBlind Creep, The ThingThe Thing, BlisterBlister, LeaperLeaper, HangerHanger, Poison MindPoison Mind, FistuloidFistuloid, Tar BoyTar Boy
11 to 13 rooms cleared without taking damage GurgleGurgle, Walking GutWalking Gut, Black BonyBlack Bony, Black MawBlack Maw, Camillo Jr.Camillo Jr., EyeEye, RoundyRoundy, Mom's HandMom's Hand, Mega ClottyMega Clotty, SwarmerSwarmer, Fat SackFat Sack, Mobile HostMobile Host
More than 13 rooms cleared without taking damage Red GhostRed Ghost, Rage CreepRage Creep, VisVis, Boss Gurglings ingameGurglings, DingaDinga, PortalPortal

Synergies[ | ]

  • Collectible BFFS! iconBFFS!: 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[ | ]

  • (in Repentance)Ace Cards: Friendly monsters are still affected by Ace Cards.
  • (in Repentance)Collectible Blood Puppy iconBlood Puppy: Either angry version of Blood Puppy will target friendly enemies as well and can drag them along with it when it charges them. Blood Puppy cannot damage friendly enemies however friendly enemies can damage Blood Puppy despite not targeting it outright.
  • Collectible Broken Modem iconBroken Modem: Broken Modem also affects friendly enemies and projectiles created by them.
  • (in Repentance)Collectible Eraser iconEraser: Enemies erased by Eraser will never show up again, hindering Mystery Egg should it spawn said removed enemy.
  • (in Repentance) Collectible Ghost Bombs iconGhost Bombs / Collectible Hungry Soul iconHungry Soul / Collectible Purgatory iconPurgatory / Collectible Vade Retro iconVade Retro: Explosions from ghosts can kill friendly enemies.
  • Collectible Glowing Hourglass iconGlowing Hourglass: Each use of Glowing Hourglass that does not move Isaac to a different room than the one he is currently in (such as the starting room of a new floor) will duplicate friendly enemies. (This is possibly a bug)
  • Collectible Holy Mantle iconHoly Mantle: Losing the Mantle will not cause a friendly enemy to spawn.
  • TickTick: Friendly enemies start with less health if they have 60HP or higher.

In-game footage[ | ]

Trivia[ | ]

Bugs[ | ]

Bug Bug! (except in Repentance) When using Extension CordExtension 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 HeartMask + Heart) will sometimes act as the heart companion for a mask already in the room resulting in an unbeatable room.

Gallery[ | ]