I have done shattered throne twice now, and killed the secret bosses once but I am still unable to claim the wish ender bow. After researching, I have found that it is because I don't have the required memento in my kinetics list, but even after creating a new character, I am unable to get this memento, completely barring me from getting the bow. I've listened to all of Sjur Eido's speeches but the slots still say "requires purified mementos," no matter what I do.