Kaijin

Kaijin was a blacksmith of the Dwarven Kingdom and the brother of Kaidou. After he was exiled from his own country he became Rimuru Tempests subordinate and helped build the Monster City Tempest he acted as a builder blacksmith and craftsmen. He also was the former commander of the Dwargon Engineering Corps. Source: Tensei Shitara Slime Datta Ken Wikia