Sky-hearts looked partially organic in nature. Their energy systems were series of root-like structures which covered much of the ship. The controls looked like blackened roots and tumours. A sky-heart was powered by both negative psychic energy (pain, distress, terror etc) and flesh of any species — so, in effect, their spaceships and other devices ate creatures if they ran low on fuel. Each Hervoken Sky-heart was equipped with a Necris, a book which acted as the starter motor for the ship. It also seemed to be responsible for channelling energy around the ship and into the Hervoken themselves. (PROSE: Forever Autumn)