Buffy The Vampire Slayer, Season 8, book 27 : Retreat, part 2

Slayers are out. Vampires are in. Mysterious big bad Twilight has just become a bigger bad -- he can zero in on Team Buffy and her army of Slayers by tracking their use of magic. But Buffy and her allies have taken their submarine -- yes, Buffy picked up one of those . . . they're a necessary piece of equip -- straight to the only person she knows with an inside track on suppressing magic: the werewolf Oz.

In the yak-filled mountains of Tibet, Oz has found his peace and formed a new life. The butter tea flows freely at the reunion, where -- among other fun reunion-y things -- Buffy learns that suppressing her demon side could be the biggest risk of all...