The Haunted Keep

Publisher's blurb:

Far out on the lonely Diminyrr Moors, there stands a ruin without windows and without doors, a black edifice amidst an endless land of fog and fear. Nobody knows when it was built or by whom. Far from civilization, only the brave and foolhardy seek its hidden gates, hidden indeed because rather than keeping anyone out, this dark ruin is said to keep spirits trapped within, like a tollbooth between the world of the living and an abyss of untold evil. But what power is so strong that it can hold back such horrors? If the legends are to be believed, that power and the prize for anyone who can conquer the evil held therein is nothing less than eternal life.