Academy City's 2nd Ranked Level 5 esper from Toaru Majutsu no Index. His ability is known as Dark Matter (未元物質, Migen Busshitsu lit. "Unknown Matter"). He often uses his powers to construct six large feathered white wings made of Dark Matter, giving him an angel-like appearance, ironic considering he's arguably the most evil of all the Level 5s.
During the events of Toaru Majutsu no Index: New Testament, Teitoku is defeated by a rogue beetle he created, which then proceeds to take over his appearance and powers, but is now a benevolent and kind person.
