Tainted Azazel is a character added in The Binding of Isaac: Repentance. He is the alternate version of Azazel but his horns are broken with blood leaking from the left stump, and his wings were cut or ripped off. Tainted Azazel is unlocked by reaching Home and using either the Red Key or the Cracked Key to access a special room in one of the walls while playing as Azazel.
Tainted Azazel starts with 3 black hearts and has his short Brimstone replaced with a room-long version that is very thin, high-pitched in sound, and deals only x0.5 damage per tick. If the charge is released before full, it will activate Hemoptysis, causing a short-range, high-knockback "sneeze" attack that will paint the enemy faintly red and deal x1.5 damage. Enemies will also take damage when knocked into walls or obstacles, and deal damage when colliding with other enemies. Furthermore, enemies affected by Hemoptysis will take full damage from his Brimstone beam for approximately 5 seconds. Unlike Azazel, he cannot fly.
In Co-Op, when Tainted Azazel dies, his ghost will maintain his Brimstone and Hemoptysis abilities. The first is weakened by the damage debuff applied to ghostly players, and the second is weakened as it has a very small size when dead.
Ipecac sneezes are harmless to Tainted Azazel, as he's too far from the sneeze to be damaged by it, but sneezes from Incubus with Ipecac are capable of damaging Tainted Azazel.
Picking up Lachryphagy as Tainted Azazel turns his brimstone into a short range attack that leaves Lachryphagy tears.