Thermosystron bombs were a type of weapon. In 2054, the Montana Republican Militia used thermosystron bombs they had bought from the Selachians in an attempt to take over Canada. UNISYC forces attempted to capture the bombs, but the Doctor blew them up. Years later, Colonel Kortez gave the last thermosystron bomb to the Eighth Doctor, who used it to destroy the Relic on Quiescia. (PROSE: Alien Bodies)