Queen of the Slayers by Nancy Holder
Willow's magickal distribution of the Slayer essence has left girls across the world discovering the full extent of their latent power. Giles races to reorganise the remnants of the Watchers Council, while the Scoobies relocate to Europe. In Rome, Buffy is drawn to a charismatic figure known as The Immortal. But then comes word that the novice slayers are being coerced to join the self-styled Queen of the Slayers -- an awesome evil who wants to claim the intoxicating Slayer essence for herself. Sent to Africa to learn more about the origins of the Slayer essence, Xander returns with chilling news. There is not enough good in the world to counteract the overbundance of evil, and that far from being averted, the Apocalypse is drawing much too near. Alliances are formed and loyalties betrayed as it comes down to slayer versus slayer, leading to an ultimate battle of champions from Buffy's past and present. And then an unimaginable gift arrives...