Fafhrd and the Gray Mouser are two sword-and-sorcery heroes appearing in stories written by American author Fritz Leiber. They are the protagonists of what are probably Leiber's best-known stories. One of his motives in writing them was to have a couple of fantasy heroes closer to true human nature than the likes of Howard's Conan the Barbarian or Burroughs's Tarzan.
Fafhrd is a barbarian hailing from the northern icy wastes. His father dead, he lived alone with his mother (leader of his clan's ice witches) who was a bitter woman, and there were rumors that she was responsible for her own husband's demise.
During an annual festival (which he witnessed for the first time as he wasn't old enough) that included a caravan of travelling entertainers Fafhrd discovered more about civilized life and grew enchanted with one of the dancers. Growing tired of barbarian life, he decided to try his fortune in one of the great civilizations in the south. He eventually met the Gray Mouser in Lankhmar.
Mouse was an apprentice to a white wizard. After returning from a quest he had found his master dead and all his possessions burned. He discovers that the Duke had outlawed sorcery and was hunting all magic users.
Out for revenge, Mouser confronts the Duke but is outnumbered and captured. However, he is able to escape due to a distraction, and conjures up a spell that causes the Duke to fall ill. The Duke's daughter (who was also an apprentice and who was made to help father against the wizard) discovered where Mouser was located but was followed by the Duke's soldiers. Mouser was once again captured and was ordered to be tortured along with the Duke's daughter, but escaped thanks to a spell. He ran into Fafhrd, while attempting to rob one of the local Thieves' Guilds and the two formed a friendly alliance.