Talk:NeoAvalon:Dungeon/@comment-31801250-20170422070947/@comment-1036329-20170424101927

As far as I can tell his nukes are tied to his dialogue, which appear to have HP triggers. He nukes once when he says "You are in my way. Leave." when lowered to below 75%, twice when he says "This is your only warning. Begone." when lowered to below 50%, and thrice when he says "Very well then. I will make this quick." when lowered to below 25%; but he only has 4 actions a turn so he can't trigger them all at once if you bring him down from full to less than 25% in a single turn without killing him.

His first move is a full party BB drain, but he doesn't buffwipe.

As stated by the previous poster he targets the party member with the lowest current HP for his nukes. If you Angel Idol that unit he will waste all of his nukes for that turn. A 100% mitigation UBB will reduce damage to 1. 75% mitigation is iffy since he can nuke multiple times a turn. Taunt will redirect (one of) his nukes to the taunter; he will most likely cut clean through Ultor without proccing the AI from his blades, though. If you have a unit with threshold AI who's been killed by a nuke, reviving them will proc it. If you have a unit that can revive, you can protect it from the nukes by equipping HP boosting spheres so that it has the 1st-3rd highest HP in your party. You can also use HP reducing spheres like Bravest Blade to force Arthur to target a unit with built-in Angel Idol.

TL;DR, Angel Idol your lowest HP party member.