Orphan of Kos
The Fishing Hamlet is truly unique setting for Bloodborne, but it's not a pleasant place. Here you'll find the final boss of The Old Hunters: the Orphan of Kos.
The Orphan's weapon isn't really an axe - the fleshy part extends like a whip. As such, you have to be careful when dodging, as it has a pretty big range. For his basic combos, you'll have the most luck dodging to your right (his left) and chipping away at his side or rear. Make sure he's finished swinging before you close in, and be prepared to step back to avoid his backward leaping attack.
He may also leap into the air for a slam attack; just keep your distance to avoid damage. If he spawns a purple orb in his hand, stay back and let him throw it into the ground. The air around where it lands will erupt in energy, so make sure you're at a safe distance.
At 50% health, the Orphan will power up, and he'll start to glide around and use altered attacks. His basic slashes and charges remain the same, but he'll gain a new slamming combo. If he starts this, keep your distance until he calms down, or zip under him as he moves forward. In general, it's much easier to dodge his attacks if you stay pressed up against him. That may sound counter-intuitive, but it works.
During this stage, he may also leap into the air and fire off several of those area-of-effect orbs. When he's up, keep moving to avoid the splash damage. Finally, he may charge up and call in lightning waves from the water. To avoid this, dash back toward the fog door: the lightning will disperse by the time it reaches you.
The Orphan of Kos may be the ultimate boss of this DLC, but he's not invincible. Be smart with your dodges, don't get greedy with your attacks, and you'll come out on top.