Monarch was the ruler of the Urbankan race.
Monarch was obsessed with discovering the secret of faster-than-light travel. He believed that by doing so he would go back in time to the creation of the Universe and meet God, whom he believed would be himself.
Monarch first left Urbanka in his ship circa 55,500 BC and arrived at Earth circa 35,500 BC, where he abducted Kurkutji and other Australian aborigines. Returning to Urbanka circa 25,500 BC, he returned to Earth circa 15,500 BC, where he abducted Villagra and other Mayans. Returning to Urbanka circa 10,500 BC, he returned to Earth circa 5500 BC, where he abducted Lin Futu and other Chinese people.
After returning to Urbanka for the last time in 731, he began his final journey to Earth, but learned Urbanka had been destroyed. With his ministers Persuasion and Enlightenment, he planned to kill all the humans on Earth with a toxin he had created, and then colonise it with what remained of his people. However, in 1981, four days before they would arrive on Earth, the Fifth Doctor arrived on the ship. Learning of Monarch's plan from Bigon, the Doctor defeated the plan with the help of Lin Futu, Kurkutji and Villagra.
After Adric immobilised Persuasion and Enlightenment, Monarch attempted to kill the Doctor, but the Doctor threw the entire sample of the toxin at him, which reduced Monarch's size to mere inches. (TV: Four to Doomsday)