Do you mean Candice? If so, Sylar never got her illusion power. He was powerless when he killed her, and therefore was unable to attain her power.I think he was using Hannah's illusion powers
I agree. Sylar has been doing this kind of stuff from the very beginning of the show, and the writers never explain it with any power. He would appear out of nowhere in season 1. Earlier this season, he was super stealthy when he attacked Claire at her house, and the writers confirmed he only had his intuitive aptitude and telekinesis when he went after her. He just does things like a horror movie villain sometimes.I think it was just for dramatic effect.