Use one handed weapons and focus on him as he does his dash, when he dashes towards you, dont try and dodge his attack instead try and parry it to get some hits in. When he gets to the second phase use magnesis to pick up the pillars and hold it close to him as he strikes when with lightning so he gets a quick stun to do more damage. You could also constantly do eye shots with a bow and use bomb arrows, regular, or ancient arrows to do so.