Prophecy Girl

In which it's the end of the world as we know it, and Buffy's looking fine.

Official back-of-box synopsis:

Buffy's future looks bleak when Giles discovers an ancient book that foretells her death and the end of the world, but she's determined to survive and party at the Spring Fling.

From the old WB Buffy website:

A HEART-STOPPING SEASON FINALE - Buffy wants to resign from her life of slaying when Giles uncovers an ancient prophesy that spells out her deadly fate, as the Master's ascension from the Hellmouth is at hand. As the earth begins to crack open, Xander, Willow and Cordelia face an army of demons and the prophetic end of the world. Meanwhile, Xander finally asks Buffy to the prom with equally disastrous consequences.

Links:

This episode's page at http://www.restlessbtvs.com/, the Restless BTVS Trivia Guide

This episode's page at http://www.vrya.net/bdb/, the Buffyverse Dialog Database

Cross-reference:

episodes in which major characters die:

• Passion
  Jenny
• Becoming (part 2)
  Buffy sends Angel to hell to save the world
• The Wish
  Another reality in which Xander, Willow, Cordelia, Angel and Buffy all die
• The Body
  Joyce
• The Gift
  Buffy saves the world a lot, rather than let Dawn die
• Seeing Red
  Tara
• Chosen
  Anya. Spike.
• this episode
  Buffy drowns, if not permanently

episodes in which vampires bite Buffy:

• Graduation Day (part 2)
  There's only one way to save Angel
• Buffy vs. Dracula
  The Dark Master has Buffy hypnotised.
• this episode
  Buffy is powerless against the Master

Cast:

• Sarah Michelle Gellar as Buffy
• Alyson Hannigan as Willow
• Nicholas Brendon as Xander
  

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• Anthony Stewart Head as Giles
• Charisma Carpenter as Cordelia
• Mark Metcalf as The Master
• David Boreanaz as Angel
• Kristine Sutherland as Joyce
• Andrew Ferchland as The Anointed One
• Robia Lamorte as Jenny Calendar
• Scott Gurney as Kevin