"The Acolyte of the Flame"

by Lin Carter
originally published Crypt of Cthulhu #36, Yuletide, 1985

Athlok, a member of the Pnakotic Brethren, comes to believe he is the subject of a prophecy who will save Hyperborea from the encroaching ice age.

Through his hubris, he ends up releasing the Great Old One Aphoom Zhah, who only hastens the ice age.

Another minor Smith pastiche from Carter.