Season 7 Episode 22
Episode aired may 20, 2003
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.
the scene in which buffy, xander, willow, and giles stand and discuss what they'll do the next day, which ends with giles saying to himself 'the earth is definitely doomed' is an homage to the very first story-line of buffy the vampire slayer (1997). the harvest (1997) ends with buffy, xander, and willow walking away talking about ways for buffy to get herself kicked out of school, and giles turns and mutters 'the earth is doomed'.