A boy of Faction Paradox once attacked the Eighth Doctor's companion Samantha Jones when she was caught up in a paradox due to her contact with the reality scar left in San Francisco as a result of the near-destruction of Earth during the Doctor's last regeneration.
The boy was confirmed to be an agent of the Faction when Fitz tried to trap him and the boy rescued himself.
At one point, the Doctor was forced to make a deal with the boy to trade one of his childhood memories to find the twisted Griffin. Later, the boy agreed to give Sam information if the Doctor would give him his Volkswagen Beetle so that the boy could scrap it and use the metal to create the same car in the past.
The boy offered to trap the current crisis in a paradox in exchange for Sam, but the Doctor rejected this offer, bluntly assessing the boy's history; born somewhere poor, the boy cut himself off from his family, became part of a gang where nobody really cared about him individually, and never thought about being anything more than the wild child until he was claimed by the Faction, who recognised him as their type of recruit as he would never care about time or the future. The boy tried to protest, but the Doctor affirmed that he was nothing more than another monster, no more special than any other monster, and Sam was far more than that and he would never allow the Faction to have her. (PROSE: Unnatural History)