Willow’s spell calls a new Slayer in Colorado Springs

Post Chosen in BtVS. Starts between seasons 6 and 7 of Stargate SG-1. Spoilers through Stargate season 9 (eventually.)

Acknowledgements: Buffy the Vampire Slayer is the creation of Joss Whedon and Mutant Enemy. Stargate SG-1 is the creation of a Brad Wright and Jonathan Glassner.