This primal isn’t your average sort of fight. I think of this guy sort of like the Ceaseless Discharge battle from Dark Souls, the non-trip version. You have to just dodge his attacks until he leaves his arms, head, hands… anything in range of your swings. For casters and ranged characters, you can keep a lock on him do I imagine you can take a shot whenever you feel safe. I break lock often on this fight just to move faster and get a better idea of my surroundings. You can roll off into lava and there is a small hole in the back you can fall into and die. Spacial awareness is the key to this encounter. Also, he can be poisoned.