What we love about this concept!
I love the idea of having a murderer or assassin as the hero. It feels a bit like Arya from Game of Thrones. There’s also a rising market for darker heroines in UFR. I love the fact that this is a banshee! I feel like they could be one of those deeply misunderstood mythos.
There are many ways you can take this concept and make it your own. You can focus on different elements of the story, you can add your own particular brand to it, and do just about anything to it. Who do you want to serve? What type of story do they want?