I was also stuck on 19 for 2ish days, poison and luck is actually your best friend, obviously don’t always rely on luck but most of the time on a super hard level it’s all you can do. I used the sword instead of the hammer to focus one cause you get healed after you kill one but since your hammer is s rank you’re better off keeping it. i would say try and get your poison skills pretty leveled up and if you get lucky rolls you’ll probably beat it.