Craftworlds are vast craft populated by Eldar. They travel through the void of space at sub-light speeds, carrying the greater remnant of the Eldar race after the Fall of their civilisation. Each Craftworld is a self-sufficient, independent realm with its own culture. Craftworlds are in many ways living entities, powered by psychic energy from its Infinity Circuit and responding in an organic way to the stimuli of psychic forces. The power within a Craftworld can be expended as light or heat, and most Craftworld technology could not function without this psychic power grid.