Golem

Biology
A Golem is a huge being that is robotic in appearance, but very much alive. Its body is fashioned out of slate-blue plate metal, accentuated by a golden shoulder and chest pieces. Atop its head is a lupine-shaped helmet made out of the same material. Large blocky protrusions run down its back, forming a spine that houses an organic motherboard.

A Golem must absorb raw metal and oil to sustain itself, but only very occasionally. Its heart is a near-Carnot engine that is remarkably efficient. With a full stomach-tank, a Golem can be battle-ready for a hundred years before requiring additional sustenance.

Golems were tinkerers by trade, but readily embrace their role as tireless fighters when the need arises.