Magna William Hon Yuen Yong was the leader of the Chapter of Saint Anthony. Magna was the title for the leader of the Chapter.
He attacked Massatoris and Betrushia. When he learned about the Keth, he wanted to allow it to escape, believing it was part of St Anthony's will. He killed Ran and Parva De Hooch before being incinerated when the Seventh Doctor activated St Anthony's Fire to destroy the Keth. (PROSE: St Anthony's Fire)