Charlie Gibbs
Charlie Gibbs was a student at Brendon Public School in the 1980s, and a classmate of Turlough. Like Turlough, Charlie was from Trion. However, his family supported the faction opposed to Turlough's family's faction in the civil war. Turlough did know any of this until he visited Earth again in 2013. (AUDIO: Eldrad Must Die!)
That same year, Rocco sold the Watcher (which was one of Eldrad's eyes) to Charlie Gibbs. It influenced him to implant it in his forehead, allowing the fragment to completely control him. The Fifth Doctor was then convinced to take Gibbs to Kastria. Using the Doctor's TARDIS as a power source, and the dust left by dead Kastrians as a conductor of that power, the Watcher restored Eldrad's physical form, based upon the likeness of Gibbs. (AUDIO: Eldrad Must Die!)