The Leader of the Bannermen and feared throughout the galaxy. He sought Delta, the Chimeron Queen, and pursued her through space and time to Earth, where he destroyed anyone who helped or hindered his quest. The Doctor tried to protect Delta and used her daughter's sonic screams to assault the Bannermen. Injured by this, Gavrok fell back into a sonic cone bomb, which he had earlier placed on the top of the Tardis to kill the Doctor, and was blown to pieces.