No Flame But Mine — Tanith Lee

The Lionwolf scrolls conclude in this epic fantasy adventure set in a snowbound world where redemption and revenge collide

The powerful mage Thryfe gropes through the steel-white snows that have covered the huddles of ruins, abandoned villages, and casualties of the White Death. He is searching for the stunning witch Jemhara, but his magic mirror can only see her past, not her present, and the sorcerer fears that a mad force abroad on the ice-locked earth is keeping them apart. At last, he finds Jemhara in the rebuilt town of Kandexa. Their impassioned and bizarre love rekindles, resulting in the birth of a boy with red hair, blue eyes, and golden skin: He is Lionwolf reborn from the land of the dead.
 
But the vicious dark lord Zzth has been burning under the sea, waiting for the moment of his inevitable return, planning for mutilation, destruction, and frigid ruin.