Hey, loving the game so far but I've spent a while stuck on the final Beast, the devil Diabolos. I have a level 22 paladin with ~2800 hp and ~1500 mp, fully equipped with mythic items and two crafted ones. I have obtained the Lava Cloak and am fully ready to confront Diabolos. However, when I battle him he immediately casts the Curse of Doom and I die within 20 rounds. I have noticed the guardians leave sigils after I kill them, but trying to use the blood vials when standing on said sigils does not yield any result. Is there an item I am missing, similar to the amulet which protects against the Curse of Negation for one of the other Beasts?

Thanks for any help.