It's a bit early to do this in the interest check, but I'm just gonna put my ideas out there so the others have something to work with.

I'm thinking I'll make a monk-type character whose fighting skills were greatest while in a tranquil battle trance. A power through enlightenment type deal. But over time, she became quite unhappy about the amount of violence she inflicted while in this emotionally detached state. So after the end of their quest, she abandoned this path of enlightenment, started drinking away her problems, and became kind of a mess. So while still a formidable swordstress, she's far from her peak and will have to overcome her internal struggle if she has to be part of saving the world again.

Now, if someone is up for it, another (preferably male) character could be her old flame, someone she had a fling with while they were saving the world together, but who she pushed away because romantic feelings seemed incompatible with the path of enlightenment she was following. The endgame for her character would be learning to be at peace with her emotions, rather than suppressing them or being controlled by them. So rekindling their relationship could be a good plot beat to go with that.