Tales From the Mignolaverse!

Sent to kill Hellboy by the Baba Yaga in Darkness Calls, Koshchei the Deathless hinted at a long and tragic life before being enslaved to the Russian witch.

Now, in a pub somewhere in Hell, Koshchei tells Hellboy about a dangerous mission when the witch sent him to hunt and destroy the last dragons before their eggs hatched.