RACK (Jeff Kober). BtVS Demon/Monster/Villain.
Rack is a powerful warlock who makes several Season 6 appearances ("Wrecked," "Villans," "Two to Go"). His den of dark magic, which moves about Sunnydale, impossible to find with the naked eye, nudges Willow off the deep end, plunging her into the spell-lust and mad-revenge that make her Season 6's ultimate Big Bad. Upon being freed of her rodent state, Amy leads Willow to Rack, who recognizes Willow's power and juices her up with a shot of magic whenever she visits him. In the end, Willow kills Rack by draining him of all his power.
The actor who plays Rack, Jeff Kober, also played psycho Zackary Kralik, the woman-hater who tormented Buffy and her mother in "Helpless."
--Caitlin Delohery