Dawn suffers more pain when her mother (Kristine Sutherland) dies unexpectedly from a brain aneurysm, which leads to Dawn resorting to black magic to try to bring her back from the grave, an action she immediately reverses upon realizing the consequences of her actions. It is eventually revealed that Dawn's purpose as The Key is to open portals to alternate dimensions — a power the hell-god Glory wishes to exploit to return home. When Glory successfully uses Dawn's blood to break down the dimensional barriers, Buffy sacrifices her own life (realizing that their blood is now the same) to end the apocalypse and save Dawn; Buffy's sacrifice also neutralizes the power of The Key, giving Dawn the opportunity of a normal life.