Atomon

The Atomon was released through an experiment using a particle accelerator on the colonial supply base Figaro Xll, by Doctor Trudo. It managed to control both Doctor Trudo and the base’s Dronebots in order to feed and grow before managing to escape the base and, taking on the body of a Dronebot, swore revenge on the Time Lords who waged war against them. (DWA: The Frankenstein Particle)