The Sheeda inhabit the Earth 1 billion years in the future. They are either the gengineered or evolved descendants of humanity, or they are the descendants of some race who comes after humanity. They are somehow related to both spiders and scorpions and possess 'crests', which give them access to animalistic powers. Since the Sheeda only become active either while invading another time-zone or while preparing to invade another time-zone, it is unlikely they will be seen again in present-day continuity.