To unlock the chest beside Rennala in the Raya Lucaria Grand Library, Elden Ring players must progress through Ranni's questline to receive the key.
After defeating Rennala, Queen of the Full Moon, within the Raya Lucaria Grand Library in Elden Ring, Tarnished adventurers might notice a locked chest sitting near the Queen on her right. Unlike other containers of loot throughout the Lands Between, this chest is locked, preventing players from accessing its contents. Searching the library for a key or speaking to Rennala will yield no results, as the solution does not lie within the world but in a particular NPC's questline in Elden Ring.
The only way to open the chest near Rennala in Elden Ring is by following Ranni's storyline by entering into servitude to the Lunar Princess Demigod. Her main storyline begins once Tarnished has defeated Starscourge Radahn of Caelid, thereby gaining access to the underground Eternal City of Nokron. After speaking with Ranni and her subordinates within Ranni's Rise, the protagonist must retrieve the Fingerslayer Blade from Nokron, hidden within a building in the Night's Sacred Ground. Afterward, Ranni will leave the tower, never to return. The player's next step is to use the portal in Renna's Rise to teleport to the northern half of Ainsel River.
Near the Site of Grace in Ainsel River Main, adventurers will reencounter Ranni; however, her appearance will be quite different from her previous form. In Ranni's Rise, the Witch's spirit resided within a human-sized, quadruple-armed doll. Now, her soul is housed within a small pocket-sized figurine called Miniature Ranni. After speaking to her several times, she will reveal to the protagonist the next step, which will soon permit them to unlock the chest beside Rennala at the Grand Library.
Ranni will task the protagonist with slaying an assassin of the Two Fingers called the Baleful Shadow. This mini-boss can be found within the cave south of the Nokstella, Eternal City, near the Nokstella Waterfall Basin. The humanoid enemy will be somewhat challenging but is vulnerable to magic and Frost-based attacks in Elden Ring. Once the fight is over, Ranni will commend the Tarnished for their efforts. Before her spirit departs for the final time, she will leave behind the Discarded Palace Key, the solution to opening the Grand Library's mysterious box.
Return to Raya Lucaria Grand Library and approach the chest to unlock it with the Discarded Palace Key. Inside, Tarnished will discover the Dark Moon Ring. From here, the player must return to Ainsel River and cross the Lake of Rot. After defeating Astel, Naturalborn of the Void, adventurers can continue onward to the Cathedral of Manus Sellus, where they will experience the conclusion to Ranni's questline in Elden Ring.
Elden Ring is available on PlayStation 4, PlayStation 5, Xbox One, Xbox Series X|S, and PC.
