Castle Shadowcrag (2007)

from the back of the book

Darker Shade of Adventure
A Gothic Castle Scenario for 10th and 11th Level Characters

The family Stross ruled the city and province of Zobeck for nearly 600 years, marrying well, fighting off invasion, and holding off a terrible curse. Then the castle was sacked in a peasant revolt, the family was hanged, and their name was erased from the histories.

All but one.

The survivor, a young boy, sold his soul to Shadow creatures that haunted Castle Strossheim... fey and flickering things never seen directly, always promising power and glory to those who would only listen. The boy heard, and listened, and obeyed the dark shadow fey. When the PCs visit the castle, they meet powerful dwarves with magic to sell. But the castle teeters on the edge of the Shadow plane, and things quickly go wrong.

The heroes can slip through the shadow into various reflections of the castle's dark past -- and they can set things right.