Join the Thieves' Guild is a quest given by Yergius in Lawenilothehl.
Requirements
The PC must be of neutral or chaotic alignment to receive this quest. The PC must also have the Pick Pockets skill prior to accepting this quest.
Description and walkthrough
Yergius will provide training in the Pick Pockets skill for PCs who do not have it, and then ask them to "prove their valor". To do this, the PC must successfully apply the Pick Pockets skill on approximately thirty monsters. Successful applications will either steal an item, or generate a message that reads "The monster does not have anything of value". The PC may also rob stores to satisfy the requirements for this quest; however, this option is much more dangerous, especially for low-level PCs.
Reward
Once the quest is completed, Yergius will make the PC members of the Thieves' Guild, which will reduce the prices at the Black Market. Yergius will also provide PCs training in Climbing, Detect Traps, Disarm Traps, Open Locks, and Stealth, for a fee.