Tristan Staghorn

Tristan Staghorn met an untimely end when he was turned into a tree by Numair Salmalin. He was one of several mages using magic to futher Yolane of Dunlath and Belden of Dunlath's plans to overthrown the crown.

Trivia:

When Numair turns Tristan into a tree, this triggers an equal but opposite reaction; that is, a tree becomes a man. Tamora Pierce later used this as the premise for a short story entitled Elder Brother. It can be found in Bruce Coville's collection of short stories entitled Half Human.