Catavolcus

Catavolcus was a warlord who once fought the Doctor. Originally a Despot from the third century, he was visited in his dreams by the demon Melanicus, who was sealed in another dimension. Under his instruction, Catavolcus performed a ceremony that allowed him to bring Melanicus back into this dimension and in return the demons bestowed great power upon him as well as the ability to traverse time. Melanicus was eventually banished again by Merlin, leaving Catavolus to roam time and space, pillaging planets. (COMIC: The Tides of Time) He eventually attacked Earth in a future time, intent on obtaining a power source known as the dragon. (COMIC: The Neutron Knights) He also attacked Gallifrey some time before its first destruction in the War against the Enemy. (PROSE: The Gallifrey Chronicles) In an alternate universe, the Time Lords knew it was a threat they were destined to survive. (PROSE: The Infinity Doctors)