Adeline

Adeline is one of the Research Hall patient found in the laboratory of said place, on the first floor of said area. She is shackled to a chair and asks the Hunter for Brain Fluid. She is also a Blood Saint according to her dialogue and can offer her blood as thanks for helping her. She also implies that she was one of the patients Lady Maria was taking care of.

In-game Information
This information comes directly from the game, or from official supporting materials.

Description
A description of facts about this subject, with minimal speculation.
 * Becomes an Enlarged Head after giving her two Brain Fluid and coming back.
 * The final Brain Fluid she needs is obtained by hitting her in her pure Enlarged Head state.
 * The Hunter receives the Milkweed Rune, a Madman's Knowledge, and two points of Insight after finishing her quest by giving her the final Brain Fluid.
 * The Milkweed Rune in japanese is called "*苗床 - Literally means ""seedbed"" or ""nursery."" In Japan a ""seedbed"" is typically an enclosed environment to protect seeds from things like bugs and diseases by placing seeds into sealed enclosures until the plants are strong enought to be transferred elsewhere.

Theories
Speculation and related theory documents, which should not be treated as fact. Most patients in the Research Hall talk about the water and the sound it makes, including the two other enlarged heads who each drop Brain Fluid, one of which belonged to a girl who was blessed with "an encounter with the Eldritch Truth". The Lake Rune description reads that "Great volumes of water serve as a bulwark guarding sleep, and an augur of the eldritch Truth. Overcome this hindrance, and seek what is yours". The same description also reads that the rune is a "transcription of the Great Ones' inhuman voices [that] ripples like a watery reflection". It can be inferred that the sound of water offers guidance to Adeline and the other patients towards the Eldritch Truth, associated with Great Ones as hinted by descriptions like the Augur of Ebrietas which a "remnant of the Eldritch Truth encountered at Byrgenwerth", as is water in general going by the aforementioned lake description and the first Brain Fluid's. The description of the first Brain Fluid listed implies that it generates eyes on the brain, which were sought by other persons looking to elevate themselves like Willem, as told by the Eye rune description, as well as Micolash going by his dialogue which, in the japanese and cut content, also mentions the "grand lake, clouded by grim". It is possible that upon receiving enough Brain Fluid, Adeline successfully ascends into a higher being, hence why she says that she "used to be nothing". She even says that she manages to see a shape, the voice of the entity, which could be a Great One, offering her guidance, which is probably an improvement over simply hearing the sound. She could have gathered enough eyes on the inside to witness the Eldritch Truth, right after licking her own blood after receiving the Brain Fluid she drops herself, since according to the description her latent potential would be reached at this very moment. The fact that she grants the Milkweed rune upon getting a revelation is another indicator of her ascencion, given the description and the many other links between plants, arcane, and Great Ones, such as the Moon Presence's second name "Flora", Willem looking like planted in soil in the artbook, the lumenflowers, etc.
 * Adeline successfully reached enlightenment and ascencion:

Adeline's dialogue and Enlarged Head description seem to insist on the depths of the water in particular. Water, in Bloodborne and other From Software games, are often associated with afterlives. The Lake rune description specifies that great volumes of water guard sleep, and Yharnam Stone that the Queen lies dead, but her consciousness is only asleep, and she can be encountered in the Moonside Lake and Mergo's Loft. "Sleep" is the keyword in both description, as it implies that Yharnam's consciousness reached the lake and nightmarish realms. The abyss in Dark Souls has an obvious water connotation in its name and is referred to as "realm of the dead" in the cut Wolnir's cup, idea that probably carried over in the game considering the description of the Tower Key which reads that the dead Firekeepers enjoy a long deserved rest in true darkness, terms that refers to the abyss going by Wolnir's related item descriptions. Déraciné also follows the idea with the river of prayer where the dead ends up, whereas the Ceremonial Tanto description in Sekiro offerings that were made by setting someone's life force adrift on the Fountainhead waters. It is a recurring pattern that the dead and the impurities that come with it end up in water. The narrator following the fight against the Orphan of Kos claims that the child return to the ocean, that he also refers to as a "bottomless sea". Micolash talks about how the grand lake is "submerged by mud" in his japanese and cut content dialogues, as does the cut Archibald character on the "the dirty mud bottom", presumably. In Dark Souls 3, Human Dregs, "heaviest things within the human body", are said to "sink to the lowest depths imaginable", in the Deep, also associated with water not only in the name but in other terms such as "Age of the Deep Sea". Emma in Sekiro talks about the Rejuvenating Sediments which is "a particularily concentrated part of Rejuvenating Waters". The recurring idea is that remains of living things are sent to the waters and sink to its depths in From Software games. Bloodborne could follow the idea, which would explain why Adeline and the other patients of the Research Hall hear the sound caused by the depths of the water, because this place in particular is animated.
 * Adeline hears the sound made by the impurities in the water: