Thief Stronghold Walkthrough - Baldur's Gate 2
The Thief Stronghold is given to you when you complete the Find Proof of Mae'Var's Treachery Side Quest. Renal typically rewards a sword and some gold when you finish this quest line unless you're a Thief in which case he'll offer the Guildhall to you instead.
I find this stronghold to be one of the more unique strongholds in terms of how it makes gold but it's also one of the shortest in terms of an actual quest chain. You can make gold using this Stronghold by sending out groups of Thieves on missions that vary based on risk. As you can probably surmise the more risk the thieves take the more gold you'll earn in return.
High risk means higher chance of capture which will lose you gold for their job that week and also cost you gold bailing them out. Another thing to note is that each week Renal is going to expect a portion of your cut, how much he wants varies from week to week and has no relation to how much you earn.
To learn how this works and also to send Thieves out on their missions you'll want to speak with Jariel in your new guild hall (pictured below).
I personally ignored this mini game in the Thief guild considering the amount of money you make is extremely small and you still have to give Renal a cut. To make matters worse, if you fail to report back to the Thief Guild each week Renal will shut it down and charge you 4k Gold to open it again. In my opinion that makes this the worst Stronghold of them all.
To start the side quests that involve this Stronghold you'll want to speak with Lathan who is found next to Jariel.
Task #1 - A Meeting With Ama
In order to start the first event from the Thief guild you'll want to speak with Lathan who can be found on the 1st floor of your guild hall next to Jariel. During this dialogue someone else named Ama will show up and give you details about your mission. We're to head over to Waukeen's Promenade during the evening hours and meet up with Ama.
When you arrive in Waukeen's Promenade (assuming it is night time) you'll be immediately thrown into dialogue with Ama. She'll tell you to put away your weapons but it doesn't matter if you actually do or not. After a little bit of waiting and a bit more dialogue you'll be approached by Sir Greshal. It turns into an ambush against you, 4 Muggers will appear and you'll have to deal with Ama and Greshal. Thankfully they're all weak and easily defeated - loot whatever they drop that you want then return to the guild.
Task #2 - Deal with the profit Skimmer
This event will begin immediately after the 1st one ends when you talk with Lathan. If it doesn't then you'll have to Rest a few days or just wait until it becomes available. You have a few different methods of resolving this quest - the correct method is to kill Darronal Gwin II who is the one skimming the profits. Any other solution will result in a negative outcome.
Completing this quest means you're done with all of the Thieves Stronghold quests. That's really all there is to it!