Boss Geniom
Base HP
Leo: 140

Yav: 140

Stage HP
Found In
The Depths
Leo: 140

Yav: 140

Dropped Items
Fast Thunder
Created by


Unlocked By
Defeat every boss.

Genion are one of the bosses that can appear in Basement. Genion are composed of not one, but two separate "bosses": One large twin with a smaller twin attached. They both have the same amount of health, sharing the health bar fifty-fifty. The large twin is called Leo and the small twin is called Yav.


  • Leo will chase the player, then periodically charge at them at high speeds. Afterwards it will stop to catch his breath.
  • When Isaac is close, Yav will shoot three tears to him.
  • When Leo is dead, Yav will chase the player, leaving a trail of green poison creep.

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