Skalesh

 was the former dictator of his homeplanet planet, Delossa. He was eventually deposed and disassembled by his own people into a raw energy that was imprisoned for eternity. Having been disturbed by the Doctor and unwittingly freed, Skalesh hitched a ride on the Doctor's tardis. Feeding off of kinetic energy, Skalesh adopted the Doctor’s clothing, creating a new body for himself. His people had long left his home world when he returned to exact his revenge. He was found guilty of a planned invasion of Delossa (now the Madrojar’s home planet) and sentenced to eternal imprisonment. (DWM: Dusty Death Cold Assassin, Designs of the Dust, A Suitable Showdown)