Astaroth Morax

 was the last surviving Colophon. He was invisible.

He was a brilliant scientist who ruthlessly sought absolute power. When the Patricians captured him and attempted to bring him to justice, he created a bacterium so powerful that it could wipe out his entire race. He developed an antidote and offered to cure his people on the condition that they bow to his tyranny. However, they refused to do so and they all died.

Morax was delighted that the Fourth Doctor and Leela arrived on Colophos. He managed to escape his prison, by tricking people into thinking he was in the explosion. (AUDIO: Last of the Colophon)