Simon the disguise...
The original Simon of Monitor was orphaned as a young child when his parents were killed in a Goblin raid. Upon maturity, he passed the Test of Knighthood and became a member of the Bear Command. Not long afterward, he became betrothed to a young woman of the city. One night they decided to ride alone to the city of Fawn. Along the way, they were ambushed by Goblins and his bride-to-be was killed. Simon just barely escaped with his life. The incident was so harrowing, however, that he decided to completely give up his fighting days. He took up the proprietorship of an inn, the Sleeping Soldier, a post which he held for many decades. By the time the Avatar arrived during the final days of Monitor, Simon was the oldest person in town.
No one suspected the horrible truth that only the Avatar would uncover. The real Simon really did die along with his beloved. A Goblin, using a magic potion acquired from a Mage of Moonshade, transformed himself into the form of Simon and lived out his life as the innkeeper. Simon supplied the Goblins with as many of Monitor's military secrets as he could, often meeting them alone near a black obelisk in the forest north of the city. The attack on Fawn Tower was successful in part because of these secrets.
The transformation was difficult to maintain, however, requiring nearly constant quaffs of a sustaining potion. Perhaps to dull the experience of his human existence, "Simon" drank heavily of Fawnish ale. Friendly and personable, no one suspected Simon in the slightest as a Goblin spy.
Another Knight of Monitor, Krayg, spotted Simon a few times in the forest, though always at a distance (i.e. never close enough to identify). The Avatar subsequently confronted Simon with some evidence and discerned Simon was lying. Abandoning his disguise, Simon attempted to kill the Avatar and his companions but was quickly outmatched. Mortally wounded, an embittered Simon lamented his long existence as a human. He also cursed Pomdirgun, King of the Goblins, since Pomdirgun had reneged on a promise to deliver the Helm of Courage to Simon. In a final act of hatred and spite, Simon went from spy to true traitor, giving up the location of the Goblin's hidden valley and the key to accessing it in exchange for the Avatar's promise to slay Pomdirgun.