The Blackmarket Quest
This one confuses a lot of people but being a gamer myself, I have gone through it many times and this is the best way I can explain it.
It begins the same way as the letter quest in regards to getting a letter and getting signed by a merchant. Then you proceed as usual towards T2 (Windhowl) and must make a stop at a new location affectionately known as Thief Town.
To get to Thief Town is a little tricky but I have faith that you will find it with some persistence:=). Once there, you need to talk to Assar, the king of thieves, you know the routine by know about name and work.
Once there, say report to him. He thanks you for showing him the report and says to get back to Lord Sunrock ASAP before he suspects something. That is what you do next, go to T2 and give the report to Lord Sunrock. After completeing this part, do not give Sunrock any more diamonds. This will reset the quest and you will hae to to it over
Now is where people get confused. You now have to wait for quite some time because what happens now is that Assar and his crew have to raid Windhowl. Once the raid occurs, Lord Sunrock accuses you of being involved in the incident. In other words, you have been called a traitor.
When this happens, return to Assar and he will brag about the raid and will ask you if you want to back out of the deal. Say no. He then directs you back to T2 to talk to the Lurker. When getting to Windhowl and finding the Lurker in the house north of the weapons dealer, say market of shadows to him. He says something about Assar and tells you to go and see the weapons dealer.
Go to the weapons dealer and say black market to him. The black market is only open at night and this is a timed quest as well.