Direct answer: the Dark Moon Ring is in a locked treasure chest in the Raya Lucaria Grand Library, and you get the Discarded Palace Key automatically when you defeat the Baleful Shadow in Ranni’s questline. Two steps, and the second one unlocks the first.
Why this is the chain that matters
The Dark Moon Ring is not an accessory detour. It opens a sealed path behind Astel, Naturalborn of the Void, and that path leads to the Cathedral of Manus Celes, where Ranni’s body waits. Completing her questline there gives the Dark Moon Greatsword. If you are stalled on Ranni’s quest, this chest is the step you are missing.
Step 1: the Baleful Shadow
The Baleful Shadow is a black wraith that appears during Ranni’s questline. Killing it grants the Discarded Palace Key — you receive it automatically, with no pickup step. A key discarded by Ranni alongside her own flesh.
- The Shadow is a glass cannon: enormous damage, very little health. Do not trade with it.
- Its attacks come from a distance and it closes fast. Keep something ranged ready.
- Do this after reaching the Shaded Castle, which is where the quest turns.
Step 2: the Grand Library chest
Inside the Academy of Raya Lucaria, the Raya Lucaria Grand Library is a Site of Grace in its own right. Use the Discarded Palace Key on the treasure chest to get the Dark Moon Ring.
The ring’s own warning is worth reading, because it is the quest telling you what it wants:
“Whoever thou mayest be, take not the ring from this place, the solitude beyond the night is better mine alone.”
Step 3: what the ring unlocks
- The ring passes you through an otherwise sealed pathway behind Astel, Naturalborn of the Void.
- That passage leads to the Cathedral of Manus Celes.
- Give the ring to Ranni’s body there to finish the questline and receive the Dark Moon Greatsword.
The reward
The Dark Moon Greatsword is a greatsword that deals additional damage through its magic negation of shields. It is one of the best pure-physical greatswords in the game and scales on Strength, which is the practical reason strength-heavy builds want this quest finished.
Wrong turns worth knowing
- Hunting for a chest in the library without the key. It is locked. The key comes from the Baleful Shadow, not from the Academy.
- Expecting to pick the key up off the ground. It is granted automatically on the Shadow’s death.
- Trying to force the Astel passage without the ring. It is sealed.
- Taking the ring and never returning to Ranni. The quest does not complete itself.
- Assuming the Grand Library is easy to reach. It is inside the Academy, which is sealed until you have a glintstone key.
Evidence status
Research-reviewed. The locked chest beside the Raya Lucaria Grand Library grace, the Discarded Palace Key requirement, the sealed passage behind Astel, and the ring-on-Ranni’s-body step are stated from current game data. The Baleful Shadow fight advice is written from the encounter’s documented behaviour. Not gameplay-verified.