[@EurmalEye] personality I would definitely think you should make the source related to the sin of gluttony although this will be a double edge sword. Darkshadows banshee would be able to take advantage of her gluttony sin but at the same time which gluttony powers you have a bottomless pit of a stomach as well as the ability to eat and digest stuff like poison, various metals and potentially even things that don’t have a physical form like fire wind or even sprits depending on how far you want to go with it. You could make her the child of a sin demon or have her have a sin demon inside herself or an item like with Rin, Cherry or the reaper or just have it as you said a blessing or course but it would not only make sense how she got that power but also let her eat more things making her more versatile and more powerful.