Kobold

The kobolds were a reclusive race of humanoid lizard-ferret-dog thingies that lived in caves under the Ashen Peaks, and they were also the single most advanced race of the Caligare Forest, at least technologically speaking. More specifically, they were particularly talented blacksmiths, and they had the closest thing to a proper industry that Blueskin had seen in this world, being able to mass produce things like plate armour and metal weapons.

They chose to armour Blueskin and his Orcs rather than face annihilation at their hands (Ch. 85).

"Kobolds are very skilled diggers and engineers. If there is anyone that can repair a collapsed tunnel, it's them." Ch. 101