Every Craftworld is built upon a skeleton of Wraithbone whose structure extends throughout the gigantic voidcraft. A similar skeletal core lies at the heart of most Eldar constructions and every one of their spacecraft. In function, this core is similar to the blood vessels and nervous system of a living creature, pumping life-giving energy around the body and also transmitting the psychic impulses that coordinate its many functions. Wraithbone is psycho-conductive, and the core of a Craftworld acts as a self-replenishing reservoir of psychic power. The invasive rib-like structures carry this energy throughout the entire length and breadth of the vessel.