drain life energies from living beings in order to access chronal energy, which he can use to open energy portals to travel through the timestream, shift objects into different timeframes, and alter the flow of time to return people or objects into a previous incarnation
Until journeying into the future as the Chronomancer, Fitzroy's only ability was temporal portals. He originally believed his power to be teleportation, until he absorbed enough life-energy to create a portal where the time difference became apparent.
Trevor is actually the son of Anthony Shaw of the Hellfire Club; 'Fitzroy' is a surname given to bastard children in the middle ages. According to X-Factor (3rd series) #50, Fitzroy's heartless personality is the result of dying and being resurrected by Layla Miller's power, returning without a soul.
Fitzroy became the White Rook as of around X-Man #23, and assumed the mantle of "Chronomancer" in Bishop: The Last X-Man #1.
The Chronomancer was apparently killed in Bishop: The Last X-Man #14. Fitzroy returned many years later in Uncanny X-Men (5th series) #20, without explanation.