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Bloodborne The Old Hunters – How to Find Brain Fluid, the Balcony Key and the Holy Moonlight Sword

Find out where to get Brain Fluid and the Balcony Key from the Research Hall, and where to find the Holy Moonlight Sword.
This article is over 8 years old and may contain outdated information

When you reach the Research Hall in the Old Hunters, shortly after defeating Ludwig, there are two items you must obtain to continue in the DLC, and one extra weapon that you need to backtrack to find. You can find a complete walkthrough of the Research Hall in our Old Hunters guide, but if you’ve been through the area and just need to find these specific items, this article will tell you where they’re located.

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Brain Fluid

There are two places in the main Research Hall where you can find Brain Fluid. The first is at the very top where you can traverse the rafters. There are several crows and a few rats in the area, but nothing too foreboding. In this area head to the platform in the middle and turn the gear to raise the platform to the very top. From here, turn back in the direction you just came and look in the far left corner to see a Brain enemy on a platform. This enemy will not attack, but if you kill it you can obtain Brain Fluid.

On the third floor there’s a Hunter that you will run into near another Brain enemy in the middle platform. You can take the hidden passage from the elevator if you haven’t moved the gear near the roof. If you have, you can take an elevator directly there. Defeat the Hunter, then kill the nearby Brain enemy to obtain another Brain Fluid item.

Balcony Key

Take both Brain Fluid items to Saint Adeline at the bottom of the adjacent elevator. Speak with her and she will request the Brain Fluid. In exchange she will give you the Blood of Adeline. You cannot accept this if you have the Blood of Arianna or the blood any other Saint in your inventory. Accept the item, then use the nearby Research Hall lamp to go back to Hunter’s Dream, effectively zoning out of the area.

Head back to the Research Hall lamp and speak with Adeline again. If she doesn’t ask for another Brain Fluid, you may have to use your Blood of Adeline, zone out of the area again, or both. Once she asks for another Brain Fluid, hand it over and she will give you the Balcony Key as a reward.

Holy Moonlight Sword

After defeating Ludwig you can equip any Church gear you may have an approach Ludwig’s head to the left of the stairs to obtain the Holy Moonlight Sword. If you don’t have any Church gear on you, activate the gear at the top of the Research Hall, then go back to the Underground Corpse Pile lamp and look to the left of the stairs to see Ludwig’s head. Examine the head now and you can obtain the Holy Moonlight Sword. If you come back to the lamp too soon, you won’t see an item on the severed head and you won’t be able to collect the item.

For more information on Bloodborne The Old Hunters, check out our Bloodborne game hub.

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Bryan Dawson
Bryan Dawson has an extensive background in the gaming industry, having worked as a journalist for various publications for nearly 20 years and participating in a multitude of competitive fighting game events. He has authored over a dozen strategy guides for Prima Games, worked as a consultant on numerous gaming-related TV and web shows and was the Operations Manager for the fighting game division of the IGN Pro League.