Prefect Zevron was the leader of Faction Klade following the assassination of the Emperor of the Needle.
His family was part of a rebellion against the Imperial Family. Her mother was executed for treason, but the Family was overthrown. He swore to make sure all of the Family was dead, so when he discovered that the baby Miranda had been spirited away to 20th century Earth, he sent the Hunters, Rum and Thélash, to kill her.
When the Hunters warned Zevron of the Doctor's presence, he and Deputy Sallak arrived in Greyfrith in the 1980s personally to kill Miranda. He failed and was killed, with his brother Ferran taking over his position in Faction Klade.
Zevron knew of the Doctor, and he and Sallak wondered if the amnesiac Eighth Doctor was from before Last Contact. (PROSE: Father Time)