there are plenty of good dark SSR kami you can pick from.
Osiris is good as she can heal your team
Dark amaterasu isn't obtainable with miracle ticket, so it's either SSR ticket jewels and luck for her, her skills are kinda like sniper shot+black propaganda+ self resistance to light and regeneration.
she can cover for black propagande and sniper shot and let you use other soul/ EX skill instead.
another good SSR that comes kinda later is tanatos that havd frame C defense debuff.
those are the 3 that at least i'm aiming for, there are other nice dark kamihime like hades if you like.
you can enter their paged in jap wiki and see what suits you the best, just remember that in the future the max debuff you can do is up to 50% so even if you run unleashed amon+tanatos+dark amaterasu/mordred/other soul with anuper shot it'll be 50% defense debuff