Aurelius

It was developed to aid in mining by detecting metals and leading miners to them. It can determine the purity and composition of an ore to a very high degree of accuracy. It can also withstand temperatures that would be impossible for humans to survive. It likes to receive gifts as thanks for its work. (basically anything made of metal, the shinier the better,)

-Lives in the tunnels

-In random areas at different times

-Anything given to it is never seen again

Although it appears and disappears randomly through the tunnels, it is rumored to have a secret base that it goes to in order to store its treasures.

Maybe a modified member of species native to the forgeworld/a replica of such?