Lilith is one of the oldest vampires and also known as "The Mother" of all vampires.
Lilith came to Sunnydale with her champion, Prince Ada, to attend Dust Waltz (a ceremony to bring back a Old One by the name of Azogg-Mon ). But in order for her to bring back Azogg-Mon, Prince Ada had to fight Lamia's (Lilith's sister) champion, Cecil. But when Lilith and Prince Ada where out hunting, Buffy killed Prince Ada. Lilith then captured Angel so that he may replace Prince Ada as her champion but after some torture she didn't find him strong enough against Cecil so Buffy stepped in as champion so that Angel, Willow, Xander & Cordelia (they where captured by Cecil's werewolves) might be free. Buffy fought Cecil and killed him with a silver dagger and doing so she freed Azogg-Mon. When Azogg-Mon accidentally killed Lamia, Lilith banned him back to the hell he came from.