It has 2 spell attacks, one with his hand and one with his sword 
. If you play close to him you will suffer his swing teleport attacks which are the ones that depending your position you’ll accept body hits, back hits or head hits. His most op attack is the one that teleports on you with the edge of his sword to create a charge strike and pierce your body. If this one gets you you are as good as dead. But this attack is the most predictable attack he has and it’s “your best” because he stays in this position for a couple of seconds giving you a great window for full combo on him. This boss great weakness is his movement speed and his predictable attacks, but don’t play it close, you’ll probably regret it even with good gear.
Keep distance, let him do his attack and then is your turn. Depending his attack your attacking windows are changing!