Yokai was the term given to a group of mechanical beings that dwell on the massive warp-infused ship Torquetum near the Eye of Terror. Commonly mistaken for robots, Yokai are in fact far more insidious in nature and seem to be mechanical beings with the bound souls of Daemons. The Yokai acted as the guardians of the Tartaruchi, who in turn oversaw the imprisonment of the Iron Oculus.
During the Horus Heresy Ahzek Ahriman led an expedition to Torquetum to retrieve the Iron Oculus under orders from Magnus. In a bloody confrontation, Ahriman and his band were successful in destroying most of the Yokai and escaping with the Oculus.