Gaston Thrillkill is a tall and imposing gray-haired bald man in his late forties. He has piercing blue eyes and wears rimless glasses, which he often peers over. Ostensibly tough, he has his weak points, such as a morbid fear of icicles, which explains his tendency to carry a hair dryer around during the winter: he melts them with it. For a long time, Amanda fears him, but she comes to find that he can be sympathetic when necessary. He is of French descent.
Headmaster Thrillkill has put away many criminals, including “Jumbo” Pinchuk, a prominent figure in the Belarus Mafia. He first appears in Book 1 of the Amanda Lester series, Amanda Lester and the Pink Sugar Conspiracy.