Gregory Leicester is the former Headmaster of The Havens and leader of a small band of Wizards, and assists Claude D'Orsay's schemes. He tried to coerce the other guilds into approving the D'Orsay-Leicester Covenant at the first Interguild Conference at Second Sisters, but failed and was killed thanks to Joseph McCauley's, Jason Haley's, and Madison Moss's intervention.

He was magically linked to 15 students at one time, enhancing his own abilities and giving him complete control over each of the Wizards.