Baltazar

Baltazar was a space pirate who had once been imprisoned on the prison planet Volag-Noc. Initially determined to compress the planet Earth into diamond, an act which would have killed off life on the planet, the Doctor and Martha Jones stopped him. Later, Baltazar went on to search for the lost ship, the Infinite via its data chips, and used the Doctor to track it down. He had a metal bird pet called Caw.

Baltazar is referred to as "Corsair-King of Callisto", although it is unknown whether this meant that he had seized power on Callisto or was merely a pirate who operated near it. The Doctor leaves this question up in the air with his line "Forget your Bonaparte, your Boudicca, even your Blackbeard..." Comparing him to a dictator, a war-leader and a pirate.

The Doctor referred to him as the "Scourge of the Galaxy". Despite this, Baltazar was notable for having a sense of humor (rare among the Doctor's opponents) and was seen poking fun at Martha and laughing while watching the Doctor awkwardly trying to pilot Caw's offspring, Squawk. (DW: The Infinite Quest)