|The subject of this article is non-canonical.
While created as part of licensed material, it has not been confirmed as part of the "real" Buffyverse continuity.
Ylisandroth was a lower being of the demon world. In order to survive on this plane, she obtained energies from others. She used the black arts to surround herself with admirers and fed off of them.
Ylisandroth approached a Sunnydale High student, Brad Caulfield, who was willing to do anything to prevent his sick mother from dying. With magics and Brad's weak mind, Ylisandroth posed as Brad's girlfriend, Sandy, and gathered his friends for her necessary feeding ritual. While posing as a human, Ylisandroth followed Brad through the day, taking classes at Sunnydale High, where she befriended Buffy Summers. Unable to understand why Sandy would hang around a jerk like Brad, Buffy thought that Brad was using magics to control her after she overheard him talking about wicca candles.
Buffy crashed one of Brad's parties and discovered that it was actually Sandy who was using magic. Severing Ylisandroth's ritual link with her intended sacrifices, Buffy watched in horror as Brad and the others fell into a comatose state, while Ylisandroth fled the scene. Calling the Scoobies to fix Brad and the others' condition, Buffy went demon-hunting. Buffy received a call from Rupert Giles, who had figured out the demon's identity from her alias. He told her that Ylisandroth could not survive on this plane without the energies that she needed from her sacrifices. There was not enough time for her to start the ritual over again, which meant that she would go back for her sacrifices. Buffy raced back to Ylisandroth's house, but arrived too late, as Ylisandroth had already resumed the ritual, and had captured her friends as protection. Unable to break the circuit or remove her friends from the pentagon circle without killing them, Buffy removed the fan blade from the ceiling and killed Ylisandroth.