Swords and Deviltry — Michael Moorcock

Here is the beginning of the legendary epic that has become a classic of fantasy adventure. At first, they seemed like an unlikely pair: Fafhrd, the white-robed princeling of the barbaric cold waste; and the Gray Mouser, a wizardling suspended between white and black magic.
Little did they realize that they were two long-sundered, matching halves of a greater hero―that they would become comrades through a thousand quests and a hundred lifetimes of adventures.
First in the influential fan-favorite series, Swords and Deviltry collects four adventure stories from Fritz Leiber, the author who coined the phrase "sword and sorcery" and helped birth an entire genre.