Fighting Fantasy
Book 28: Spellbreaker

Rassin Abbey has guarded its arcane treasures for centuries. But when their Black Grimoire spellbook is stolen, the land of Ruddlestone is plunged into a crisis of epic proportions. Should the legendary Casket of Shadows be opened, the Infernal Beast will be unleashed to wreak its terrible carnage across the Old World. On the night of Shekka's Moon, scant days away, this will surely come to pass. Unless, that is, one brave hero can retrieve the Black Grimoire in the nick of time - a hero like YOU!