This might be the first comic publication for this cover image. It was also used on the French novel Dans un Monde Inconnu (Presses Pocket, 1974) #820 by H.G. Konsalik.
Origin of Doctor Strange.
This story is set in Conan's Hyborian in the kingdom of Aqilonia.
The first page of this story has been removed, including the original title 'To Dream-- Perchance to Die!' and credits.