The Blighted Ovum is the posthumous version of Gemini, added in the Wrath of the Lamb DLC. He appears in the Catacombs and, rarely, in the Cellar. He has a higher chance of appearing if you have killed Gemini before.
The Blighted Ovum spawns already separated, similar to the green Champion version of Gemini.
The larger sibling appears as a mangled and bloody zombie, with parts of the skull eaten away. He leaves behind a trail of Red Creep as he moves, which damages Isaac for a full heart. Unlike Gemini, he will constantly pursue Isaac, not stopping for breath after charging.
Meanwhile, the other half appears as an invulnerable spirit, and is passive unless Isaac gets in his line of sight, in which case, he fires a blood beam similar to Brimstone. He tends to stay floating in the area it spawns in, not moving around much.
Upon death, each half shoots radial blood shots, similar to when Steven is killed.
- In medicine, a blighted ovum is a pregnancy in which the early pregnancy appears normal on an ultrasound scan, but later no visible embryo develops. This likely refers to the smaller twin being dead (a spirit).
- Its boss-screen artwork differs from the in-game sprite, as it has a beady, black eye and a grey body, while in-game, it is eyeless and has a blood red body.
- The large bite on the top of the head is on the opposite side on the artwork and sprite; this is probably unintentional.
- He is also missing his jaw like Daddy Long Legs and Headless Horseman.
|Basement||Larry Jr. • Monstro • The Duke of Flies • Gemini • Steven • Famine|
|Cellar||Widow • Pin • The Duke of Flies • Famine • Gurdy Jr. • The Blighted Ovum|
|The Caves||Fistula • Peep • Gurdy • Chub • C.H.A.D. • Pestilence|
|Catacombs||The Husk • The Hollow • The Blighted Ovum • The Carrion Queen • Peep • Pestilence • The Wretched • Gurdy Jr.|
|The Depths||Loki • Monstro II • Gish • War • Mom|
|Necropolis||Mask of Infamy • Daddy Long Legs • The Carrion Queen • The Bloat • Loki • War • The Wretched • Mom|
|The Womb||Scolex • Blastocyst • The Bloat • Death • Conquest • Daddy Long Legs • Triachnid • Teratoma • Mom's Heart • It Lives|
|Utero||Teratoma • The Bloat • Death • Conquest • Daddy Long Legs • Triachnid • Lokii • Mom's Heart • It Lives|
|Sheol||The Fallen • Satan|
|First to fifth and seventh level||The Fallen • Headless Horseman|