Anzor

Anzor was a Time Lord who attended the Academy at the same time as the Doctor.

Biography
Anzor was the school bully in the class of the fourth millenium at the Academy on Gallifrey. He had a device called "the galvanizer" which was a short blue rod with a glowing orange tip. He used the galvanizer on his classmates to ensure that they did as he said. He particularly bullied the Doctor, forcing him to do his navigational homework and on at least one occasion using the galvanizer on him, as he later threatened to "revive your memory of my galvanizer" to terrify the Doctor.

Only one person ever stood up to Anzor, a boy named Cheevah. Anzor sealed Cheevah in a block of crystal and dropped him from a great height into the school yard as a punishment. The Doctor later told Peri how Anzor had forced the rest of the children to laugh at this at the threat of his galvanizer.

Years later he encountered the Doctor's sixth incarnation, who was still traumatised by his experiences with Anzor at the Academy, and forced him into a locked orbit above the planet Magnus. However the Doctor betrayed his old classmate by causing Anzor's TARDIS to fly back to the big bang slowly, knowing his foe did not have the knowledge to reverse it. (BFA: Mission to Magnus)

One account claims that the Doctor killed a bully who was tormenting him and the Master. It is possible that this bully was Anzor, and the Doctor's actions may have caused Anzor to regenerate. (BFA: Master)

Other information
His TARDIS was a type 60 and one form it took was an oak tree.