Buffy the Vampire Slayer season 7 episode 22
Episode title: Chosen
After killing Caleb, Buffy conceives a plan to defeat the First once and for all. Willow invokes a magic spell that alters the ancient Slayer spell and gives Buffy the allies she needs to fight the Uber-Vamp army. An epic battle ensues and several good friends are lost. At the end, Buffy faces a completely new problem -- one she's glad to have.
