Take hammer from blacksmith
"Take hammer from blacksmith" is an objective in the quest The Bloody Harvest in TK Bahas Bloody Harvest DLC
Head into The Infested Forge. You will find Sully The Blacksmith. The problem is that Sully will immediately attack you with Flaming Hammers.
Sully will hang back some and mostly just throw his hammer at you. If you get close, he will start unleashing fiery blasts around himself. Just be wary of those.
When defeated he will drop The Blacksmith's Hammer. Approach it and grab it.