if you are trying to get the cool animation when you do his fight without taking any damage, good luck
currently trying and i dont think i have ever given this many attempts on a single boss
(i have 8 ADP using sacred chime hammer +5)

When he does his upwards slash move, just roll backwards. When he does his stab with the magic around his sword, roll right not left. Going left will have a high chance of getting sucked back in to the stab animation.

This page doesn't mention it, but I'm pretty sure his sword gets a damage boost as well as doing bleed after buffing it from catching you with his dark-imbued impaling thrust attack.

immune to poison

Hand it over that thing, your cool armor, for my newest drip

Use the two invocations to distract him while you strike him from time to time with a physical weapon. Block with your shield or roll/dodge untill they focus back to the summons. Embue with dark resin for better result. Use raw weapon if you are "mage" oriented so that you can deal a decent ammount of physical damage. One summon survived.

Not too bad if you stay close to him and watch the positioning. It gets nasty if you try to get some distance to heal.

The music for this fight goes so damn hard

this guy would be insanely hard if he had a moveset of sekiro's bosses

Swing a thin Katana blade, but has hitboxes of a hammer... ::sigh::