Paige is a major antagonist of the series.
Originally a human that went to the same school as Seth, she inexplicably fell in love with him, even before he became a werewolf. After he became a werewolf, Paige forced Seth to turn her. She then began to kill girls she suspected were dating Seth, wanting him all to herself, even going as far as horrifically murdering his mother, older sister, and his pets.
Eventually, Seth became a werewolf-incubus hybrid, overpowered Paige on a Blood Moon, and put her in an underground tomb with a magic spell that not only trapped her, but would prevent her from transforming as long as she stayed there.