Koloss

A species of blue-skinned, red-eyed humanoid warriors of enormously varying size — from five-foot scavengers to ten- foot-tall giants — that the Lord Ruler raised as the empire's heaviest shock troops and kept far from cities. Their bodies grow continuously through life, but their skin does not; the eldest tear bloodily at the edges of their eyes, mouths, and chests, and most die when the swelling body finally overwhelms the heart. Their society — if it can be called that — is run on sudden, casual murder between near-equals, with the survivor stripping the weapons and the small leather pouches the dead kept tied to their straps. They have no economy, breed and grow quickly, and will eat anything — meat, grass roots, ash. They obeyed only the Lord Ruler during his rule, and nobody yet understands quite how. MB1:WoA:Ch 19

The Lord Ruler's monstrous shock troops — larger than men, used at his command to crush rebellions where his soldiery cannot. Kelsier brings them up at the planning table as an obstacle the crew will have to think around. MB1:TFE:Ch 4