i don't know if this is a bug, or a strategy request,
but in the fight against the Antiguardian (where we are locked to the Ultraguardian armors and shield), the armor locks us into a 100% darkness resist modifier.
Is this intentional? because it makes the fight unnecessarily difficult if we cannot defend against a mob that hits over 1000 with that resistance value.
I believe it's bugged. It hasn't always been that hard. I suggest using a -50% Darkness misc. That'll make it possible to win. Also go in with some potions. I can't remember if it works, but you can try changing your no-drop element to Darkness.