The morning came hard. Lirielle woke to find Jesse standing over her, dagger drawn, finger to his lips. Downstairs, Mama's voice was carrying loudly through the floorboards, clearly a warning to the party. City guards had come for her on a charge of treason. The party got to their feet quickly and scrambled for the window. Landor caught a boot on the sill and slammed flat onto the roof.
Momeline stayed back. When a guard came pounding up the stairs she dropped him with a word of sleep magic that Lirielle had told her would work well. She locked the door behind him, pressed a wine bottle into his hand for the rest of the watch to find, and dropped down to eavesdrop. The charge against Mama was vague (treason could mean almost anything in Khasim's Crown) but the destination was specific: Shefir's Prison, the cruelest cells the city kept. Ferinthria cast Seeming over the party, dressing them in stolen faces from the streets they had walked the day before, and they set out for Shahzir's Library to find a way into the ancient prison.
The archaeological section was off-limits without a pass. Lirielle produced the diviner's coin she had picked up weeks before, and the librarian's apologies came in a flood. In the lower stacks they found a statue of Shahzir they were certain held a secret. They touched it, spoke to it, showed it the Crown of Judgement; Lirielle even put the Crown on, and was thrown straight back into the fall of Valengarde for her trouble. The statue gave them nothing. The library, at least, gave them a blueprint of the prison.
On their way out, High Magister Selene Anvari stopped the party in the hall and asked who they were, saying that she did not recognize them. They bluffed straight through her, feigning shock and saying "you don't remember me, that's embarrassing" and walked out of the library before she could respond.
At the prison the coin worked again. They played power games with the guards, leaned hard on the diviner's seal, and Momeline slipped past the distraction into the cells. She found her brother Milo in one of them, picked his lock without a sound, and pulled him out. While she worked, Landor slipped into the storage room and came back out with a suit of elven chainmail and a spellguard shield, both bearing the sigil of an old Balandelian royal house. Milo had a message from Mama: find out why Tassir had set this all in motion, and find out what was about to happen in the Oasis Vault.
The coin got them into the vault as well. They watched Anvari go down ahead of them in one of the fish-shaped submersibles and followed in the next. In the offices, Dravencoles spotted a confiscation bag labelled Belongings under Investigation: Ferinthria Everflame. The real Ferinthria recognized nothing inside it. Lirielle named the carved stone among them for what it was: a scrying focus. Anvari passed close enough to brush against them in the corridor and never looked up. In a sealed sanctum at the heart of the vault they found the Book of High Magisters resting on its pedestal, and through Misty Step and Otiluke's Resilient Sphere they lifted it clean.
The party is still deep underwater in the Oasis Vault. What do they do next?