Front Towards Gamer's video: Bloodborne Guide: How to defeat The One Reborn

The instant this fight starts immediately run forward and to the right dodging those shots and punches. Head to the back of the arena and up the stairs. The key to this fight is to kill the 6 mages atop the level first. Otherwise they bombard you with fireballs while buffing the boss. Head on upstairs kill all three on one side and the three on the other. Once there all dead lure the boss over the middle section of where you fought the mages. Once he raises his head hit him with a drop attack which should get hits several hits as you fall. Once you land attack the base until he is stunned then go for the head. Avoid his kicks and corpse throwing but most of all keep an ear peeled for when he charges his magic attack. This is a devastating knock down attack you want to avoid that at all costs. If you need to heal run out of there even head back to the stairs if you need a moments respite. Return to attack the base until he's stunned then go for the head. This walking pile of corpses won't stand a chance if you get him stunned.