Bonesinger

Bonesingers are Eldar artisans, weapon crafters, architects, masons, IT technicians, janitors, coffee brewers, firefighters, yadda yadda yadda. They possess the unique ability to shape the Wraithbone, without which the Eldar would be armless failures.

They practically never see combat, unless a Wraithlord breaks a leg or a Falcon's weapons go derp. Still, they managed to be in Dawn of War as the Eldar builder unit.