Madrigor was a renegade Time Lord.
Biography
In his youth, Madrigor was brilliant and clever and was the youngest on Gallifrey to ever be appointed a Time Lord. Madrigor was greedy, however, and used his powers for his own ends, and not for the greater good. Eventually, the Time Lords found out that he had been travelling through time and space to other planets and stealing from them. He was tried for his crimes but never punished, as he was able to escape before his sentence was carried out.
Madrigor made a home on Lunargov III and lived a nomadic existence. From there he planned to steal a Time Ioniser from Gallifrey, and overthrow the planet's rulers. He then wanted to use the Ioniser to rule the major governing bodies of the galactic powers. The Third Doctor and Sarah Jane Smith were sent by the Time Lords to find him and bring him to justice. The Doctor met with Madrigor and learned of his plans, then sent the planet to somewhere where Madrigor couldn't pose a threat. (PROSE: The Time Thief)
According to the Doctor, Madrigor had a love for beautiful things.