Faith Lehane, the "rogue" Slayer in Buffy the Vampire Slayer, provided a foil to Buffy, and her story continued after the TV show's seventh season completed, moving into Dark Horse's comic book adaptations.
Played by their status and privilege as Slayers as something that set them apart from everyone else, two against the world, sharing a burden that nobody else could understand. Beyond that, Faith possessed a more aggressive nature and seemed to enjoy hunting and killing on patrols, where Buffy deemed it a necessary evil, for the greater good.
This difference often put the two at odds, and in season three, defeat the First Evil in season seven. Faith and Buffy trained the new Potential Slayers together, and while the air was never completely cleared between the two for their tumultuous past, they seemed to be in a good place - both alive and no longer sharing the burden of being a Slayer in a solitary manner - after the series finale. Faith's story continued in the Dark Horse comics, which picked up where the show ended and has gone through a twelfth season.
What Faith Has Done Since Buffy The Vampire Slayer Ended
The season seven finale of Buffy the Vampire Slayer made mention of a Hellmouth in Cleveland; Faith kept her connection with Robin Wood, the son of a Slayer, open when he traveled to Cleveland to lead a group of Slayers there. Though Faith never was the type for drawn out, romantic connections, it always seemed like she was genuinely fond of Robin. Though always somewhat of a loose cannon and a wild card, Faith's love of being a Slayer faded over the years, with her taking on the occasional job to help Robin or Giles, who contracted her as an assassin to kill another rogue Slayer who was a potential threat to Buffy.
Faith's friendship with the rogue Slayer, Gigi, ended up Giles, Faith took Angel's side and decided to help him through his guilt and pain as he had once done for her, then settled down in London.
Through her friendship with Angel in particular, Faith found a new sense of purpose and maturity - it became her goal to keep Slayers not only together, banded together and strong, but help them realize their purpose and keep them from making her old mistakes. Faith has always possessed a great deal of guilt and self-hatred, similar to Angel's brooding nature, where he feels like he can never fully atone for his past sins. It made them good partners throughout the comics, and added a lot of depth to Faith's character. Ultimately, Faith ended up with the remaining of the Scooby Gang in San Francisco, and became part of a supernatural police division with none other than Buffy herself in the most recent Buffy the Vampire Slayer comics.
