Flawlessly terrible.
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Incoming Xenoblog
Ahem jokes aside, I am now at "that one boss" in my Xeno adventure that likes to resist any physical damage so how should I go about damaging Aihtirol?
Corvo should know what boss I'm talking about.
So the characters you want to use are Seventh and Melia, as Seventh has a lot of magic-based attacks and a high damage output and Melia is of course the team wizard. I believe I had Sharla in my party because I could never quite figure out how to survive without someone constantly pumping me full of HP. You may consider playing as Melia during this fight and letting her keep the party's buffs going, especially regen, but I believe I played as Seventh because
she
No matter what happens, you will wind up in the green vats on the side of the arena, and they will kill your party a whole lot, so avoid them, and run out of them when you do wind up in 'em, as they're way worse than the boss.
But yeah, I hated this fight. I hadn't yet done my end-game grinding, though, which is something I would recommend you get started on now: don't fight her till her name appears in blue or black or whichever instead of red or yellow.