Xeriphas was the homeworld of the psychic Xeraphin race. Back around 140 million years BC, Xeriphas was caught in the cross-fire of the Vardon-Kosnax War and devastated by radiation. The fleeing Xeraphin merged into a gestalt and left for Earth. By the early 1980s Xeriphas had returned to normal and The Doctor sent the Xeraphin to Xeriphas which the radiation has cleared up.