The Elysians were a secret sect within the Time Lords.
They were clones created from the Time Lord Academy dropout Xanti, the son of Uriel. They were made secretly by Overseer Luther. These clones were part of a plan by Luther to take the Watchtower and rewrite history, turning himself into a god to rule Gallifrey. This led to Xanti discovering he was being stalked by the Elysians. He believed only the Eighth Doctor could save him. When the Doctor arrived, the Elysians teleported in and tried to kill him but the agent Shayde saved him, gunning down one of the assassins. The others escaped with Xanti and Izzy Sinclair.
The Doctor later discovered the captive Elysian was a clone of Xanti. Through Uriel they learnt of the Final Chapter. Later, when Xanti was placed in the Watchtower by Luther as part of his plans to become the supreme ruler of a militaristic Gallifrey, he turned the Elysians against Luther, ending his threat to the universe. (COMIC: The Final Chapter)