She first appears in season four. She then possesses a girl named Kim and remains. Season seven has not come out at the time I am writing this so something could happen.
There are two main characters possessed, the first being in Emerald Secret. A character names Ghost possesses Kim to try and get closer to Zane. Ghost turns out to be a helpful character in the story. The second possession is on Travis in season six, When Angels fall. I think the possession was done by Terrence but it might have been Michael (the Snake-Eyed Man). It was mainly used to solve an argument between Travis and Katelyn.