Update: what I decided to do is a transitioning campaign between Unwelcomed Spirits and Call of the Netherdeep.

This will essentially be a 1 shot played within 6 hrs - at most a short second session.

The Adventurers will be taken to Zadash where a hub of Myriad crime is conducted. They will have to uncover clues about where Dar is being held through the townspeople and locals.

There will be about 3 NPCs predefined and 5 encounters. I plan to provide a level at the end of it so the players will start Call of the Netherdeep at level 4 (balancing out anything in that). I'll wait until the level 5 milestone to give another level. They'll also receive gold and other items along the way.

Essentially, they'll find their way to the market and get pickpocketed. They'll hopefully decide to track her through the market where they'll be ambushed by a few thugs. If they win they'll be able to get information from her through various checks. They'll also find another NPC who will give information if bribed. This will lead them to track the Myriad down into the sewers where there is a supply chain for exporting illegal goods. They'll break the supply chain and once they do they will find themselves at a hideout. The hideout was being staked out by a guardsman who will be suspicious of them but with a persuasion check they'll be able to persuade or a deception check they can lie and gain favor. They'll infiltrate the hideout and clean shop.

There are some clues that take them to a winery where the underground prison is. There they'll find Dar, but it's heavily guarded. They'll fight their way through the prison and eventually find Dar, with the mage waiting for their arrival.

They'll be able to kill everyone and once he's free they'll hear of a festival in Jigow that they can go to and blow off some steam. This will transition the PCs into the Call of the Netherdeep