The Castle of Lost Souls

From the back cover: Beyond the hills and haunted swamps towards the sunset lies the grim castle of the arch-fiend Slank. For centuries this hell-spawned demon has plundered the souls of mortal men, gathering them to his terrible abode to dwell in eternal torment. Now secret magic that can destroy Slank is known at last. You agree to undertake this perilous adventure - but can you rid the world of the demon’s evil shadow, or are you merely destined to become the next of his victims? Golden Dragon Fantasy Gamebooks #6 This adventure first appeared in White Dwarf #52-55