Koschei the Deathless is a villain in the Hellboy series.
Koschei in the Hellboy universe was the slave of Baba Yaga and he is lterally Deathless as Baba has his soul being seperated from his body that Baba currently has.
A Dragon killed him and later takes his soul after Koschei was revived by Baba in hopes to finally die as he is tired of his immortality.
He was contracted by Baba Yaga into Killing Hellboy. After Losing to Hellboy He tells Baba to let go of her grudge because the goat has his soul Now. The Goat that has his soul later takes it to Hell where Koschei follows him in hopes to reclaim it.
He later Encounters Gomori along his path in a desert and makes his way to the seashore where he also met Hellboy in a bar and they share stories. Hellboy explains how Hell changes his time there and leaves to conitinue to look for his soul.
Powers and Abilities
Kosechei is a master swordsman able to go toe to toe with Hellboy and the other BPRD agents as well as the ability to use magic.