Sunday's accessory quest is pretty dang dangerous. You still get the trash, the mid boss and the last boss but their elements are randomized by stage, trash mobs won't be mixed. Encountered thunder trash, water mid boss and thunder final on my attempt using my light team. Ended up using an elixir. Will probably just run rank3 for the rest my uses.
I'm not sure if it's worth the gamble if you don't have an extremely strong dark or light team to be honest. The risk of encountering an elemental weakness. Unless you're a whale who can use an elixir every run if needed. Though you could always get lucky too.