The Unholy Grail

The Unholy Grail is a sword and sorcery novella by Fritz Leiber, recounting the earliest adventure of the Gray Mouser.

First published in 1962, it is the nature of a prequel, as Leiber had by that time been chronicling the pair's adventures for thirty years.

His young apprentice, Mouse, still wavering between an allegiance to black or white magic, returns after a long quest, but finds his master dead and their house destroyed.

Badly wounded, Mouse is discovered by Ivrian, the Duke's daughter, who has also been secretly studying with Glavas Rho.

Using the blackest of black magic, in the knowledge that it may rebound on him, Mouse manages to aim a spell at the Duke, using Ivrian as a focus.