"Use forge hammer" is an objective in the quest The Bloody Harvest in T.K. Baha's Bloody Harvest DLC
Walkthrough[edit]
With the 3 Enchanted Skeleton pieces placed you need to use the Blacksmith's Hammer to strike them 3 times. Just look where the Hammer's silhouette is and interact with it. This will cause the hammer to appear and strike the iron with the key pieces.
