The Hellions were a biker gang formed mostly by demons of the same species, as well as a few humans. These demons were humanoids with wrinkly skin, sharp teeth, pointed ears and no nose. In addition, their faces were adorned with tattoos and leather straps attacted to their skin.
The Hellions were led by Razor and enjoyed raiding and looting towns, though only targeted small backwater ones that they considered vulnerable. Even though the gang had human members, vampires weren't allowed due to their inability to go out during the day.
They came after Sunnydale when they learned it wasn't protected by the Slayer, but a robotic duplicate. Their raid was shortly taken care of when the real Buffy was resurrected and killed many members.