Koel Paddox was the leading necrologist of the year 3012.
After witnessing the death of his parents in a shuttle accident when he was six, Paddox became obsessed with finding a way to change his history. Learning of the unique existence of the Arboretans, Paddox set out to find a way to artificially duplicate their ability to live their lives over again in the hopes of sending himself back to his birth and averting the accident, apparently justifying his genocide on the grounds that he would then have undone his crime.
Although Paddox succeeded in his quest — although his experiments nearly released the powerful Repulsion on our universe before it was stopped by the Fourth Doctor — he was unaware of one crucial detail; as a human, he naturally lived inside time, where Time Lords and Arboretans lived somewhat outside of it, and he had therefore doomed himself to be trapped for all eternity in a horrific time loop, condemned to watch his parents die and commit genocide in a pointless attempt to change the past over and over and over again. (PROSE: Festival of Death)