Vault of the Ninth World is both the name of the floating head that manages the Warehouse in the Lower Ward, as well as the name of the warehouse itself. Vault of the Ninth World is cheerful and eager to provide high quality customer service. In spite of this, it's not clear that Vault of the Ninth World is sentient as it seems to follow a pre-programmed script when interacting with The Nameless One.
Conversation[]
Vault of the Ninth World tells TNO that the warehouse serves all sentients of Sigil, with their motto being, "When one world just isn't big enough!" and claiming their customer service is known throughout the planes. It confesses that the name of the warehouse is an exaggeration and that the owners likely chose it because they thought it was clever.
If TNO asks to store something in the warehouse, Vault of the Ninth World tells him the warehouse is full. If TNO points out that the warehouse is huge, Vault of the Ninth World acknowledges the contradiction and tells TNO there's something fishy going on.
If TNO asks to claim something and has a 15+ intelligence or wisdom, he can tell Vault of the Ninth World he's looking for a large bag of coins. Vault of the Ninth World will ask TNO how many coins are in the bag to verify ownership and with a high enough wisdom, TNO can intuit that 1123 coins "feels right" (receive 1123 copper coins). If TNO has the quest to help Trist and has spoken to Lenny, he can tell Vault of the Ninth World that he "gave Pikit the laugh" which prompts Vault of the Ninth World to give TNO the Scroll of Evidence and the Loan Document.