Koschei, also known as Koschei the Deathless, is a warlock born in the mid-11th century.

 

He befriend Baba Yaga and the witch taught him how to craft a soul key which he used to become immortal.

 

In 1171, Koschei seized control of a warrior tribe and became their Khan, leading his people into many raids of the western lands.

 

After his tribe faded, Koschei moved west and built and underground lair where he continues to practice his dark magic.

 

 

Image from Trick or Eat 19:  The Soul Key

Koschei playing with soul keys.