In Preppies of the Apocalypse, Silvanus is a changeling who helps Kit Garrett and Ashley Thorne, only to betray them to Conrad.
Silvanus
A man entered the hotel through the revolving door. Or… not a man. He could only be another changeling, a demon yuppie with close-cropped hair and wire-rimmed glasses. A long tail stuck out the back of his tailored slacks. Sharp points of bone jutted out from tidy holes in the elbows of his crisp blue button-down shirt.
