Trevor is a mage, and one of Veneficus' many apprentices. In the first few chapters, Veneficus stops by Villageville to check in on him, but finds him missing. He therefore offers a sidequest to the main character to find Trevor and ask him to return. Trevor can be found meditating in Cromwood Cave. When informed of Veneficus' presence, he teleports back to Villageville.
In addition to the reward offered by Veneficus for this quest (a SoulStone), Trevor re-opens the magic shop and spellforge on returning to Villageville, allowing them to be accessed by the heroes.
Trevor is shown to be able to sense people with his mind. This ability likely has considerable range, since he was surprised he was unable to sense Veneficus. He is also seemingly able to teleport at will.