The Old Hunters DLC ends in the Fishing Hamlet — a coastal village of half-fish, half-human creatures who have been brutalized by hunters for generations. The reason is buried in item descriptions and NPC dialogue: hunters came here to harvest the eyes of the Hamlet’s residents to create Paleblood, the substance the entire game’s framing device is built around.
The Great One called Kos, or Kosm, washed ashore near the Hamlet long ago. The villagers revered the corpse, and over time absorbed its cosmic influence. When the Healing Church discovered this, they sent hunters to extract umbilical cords and eyes from both the corpse and the villagers — a colonial atrocity dressed in medical language.
The orphan that erupts from Kos’s corpse when you approach — the final boss of the DLC — is the child of the Great One, and its screams are the audio recording of an actual infant, pitch-shifted and layered. Miyazaki confirmed this was intentional to maximize discomfort.
The player character in Bloodborne is, by the end of the DLC, complicit in what the Hunters did to the Hamlet — you are there to put down what was awakened by your predecessors’ violence. The Hamlet is Bloodborne’s most complete expression of the game’s core theme: that the pursuit of forbidden knowledge creates suffering passed down through generations.

I’ve put 200 hours into this game and never caught this. The developers really reward the obsessive players.
Currently on my first run and now I have to go back and look for this. Worth the detour.