You must first destroy his armor. It is the white bar at the bottom of his heath bar. Equip your spear then use Blood Drunk. You only have a limited amount of time before he calls other Immortals. It would be best to try to get his armor down as much as you can before he calls them. Make sure to block his attacks as much as possible, and when his razor hands turn blue or red run away. You cannot block those attacks. If he calls other Immortals, ignore the Immortal King for a while and kill his friends. It is best to kill them with dual swords. After you destroy his armor he will jump on top of a cage and shoot his hands at you. You cannot block his hands. Run behind the pole with some dead bodies attached to it that is close to the cage he is standing on. When he shoots his hand at you, it will get stuck to the pole. Quickly run to another pole that is beside the one you were just hiding behind. He will shoot his other hand at you and it will also get stuck. Once this happens, run into the open and throw a spear at him (hold Circle + Square + X). It will go directly into his chest and do alot of damage. Keep on repeating this process three or four times until he is dead.