Malador was, according to legends on Serenity and even Gallifrey, an immortal and indestructible being of pure evil. He created the Melkur to be his silent army.
Malador's perception of good equated it with guilt, and he claimed to have had his conscience surgically removed, allowing him to act with no concern for the consequences. On the planet Serenity, he created the computer Prophecy and ruled until he was tricked by his subjects into imprisoning himself in a stasis field. In the following centuries, the Melkur fell into dormancy. (AUDIO: The Guardians of Prophecy)
The Traken Union had protected its people since the time of Malador, (AUDIO: Hexagora) until its destruction in 1981 (TV: Logopolis) leaving only Serenity, later serving as the head of the Benign Union.
Millenia later, Auga's attempts to deactivate Prophecy in the Tomb of Malador accidentally awakened him. While Prophecy's shield of goodness was destroyed, awakening the Melkur, Malador planned to reverse the process and project a shield of evil that would spread across the universe. The Sixth Doctor modified Prophecy's power source to amplify the energy in his tomb, causing a dimensional fracture through which Malador and the Melkur he had summoned were pulled, removing them from the universe. (AUDIO: The Guardians of Prophecy)