He was the blacksmith of Thirsk mead hall before the rieklings attacked. While in the camp he states that he is worried about his forge, and wonders what the rieklings are doing with it. After the quest is complete, he becomes a regular weapons and armor merchant.
Help retake Thirsk from the rieklings.
Kill him and his allies for the rieklings.
Halbarn can be interacted for a quest which is going out and collecting ten Stalhrim and fifteen Ebony Ingots to go back into business. After completing the quest, Halbarn becomes a candidate for marriage.