The Defias Brotherhood
Gryan Stoutmantle knows someone who knows someone, if you know what I mean. He did a favor for this guy, Wiley the Black, and figures to cash in by having you find out more about the Defias Brotherhood from him.
It's risky for him, but he does owe Gryan a favor. Wiley pens a note for Gryan, and asks you to return it to him. (You were headed that way anyway, weren't you?)
Back at Sentinel Hill, Gryan reads a reference to the Stonemasons. Gryan doesn't know anything about it, but he does know someone who might. He asks you to take the note to Master Mathias Shaw, at SI:7 in Stormwind's Old Town district.
Master Shaw is able to fill in a few blanks about the Stonemasons. He writes up a report for Gryan, and asks you to take it back to him.
Edwin VanCleef had been leader of the stonemasons who rebuilt Stormwind. Gryan doesn't want to believe that VanCleef is the power behind the Defias on just this little bit of evidence.
For now, then, he asks you to help track down the entrance to the Defias hideout. His scouts reported Defias Messenger whose mail bag would provide important information. Gryan asks you to waylay the messenger (in the name of the law, of course) and bring back whatever messages you can find.
The messenger resists, of course, but you get the messages anyway.
Gryan Stoutmantle decodes the messages, and determines that VanCleef is indeed the leader of the Defias. But while you were out gallivanting, Gryan's people have captured a member of the Defias gang that is willing to sell out the rest of the gang to save his life. All you have to do is... make sure he stays alive long enough to show you where the hideout is.
The Defias Traitor leads you through Moonbrook to the mines on the south side of town. You have to ward off pretty much the whole town, but you get there, nonetheless. Having done his part, he fades off into the underbrush, while you return to Stoutmantle.
While it saddens him to do it, Gryan must ask that Edwin VanCleef be assassinated for the greater good of Westfall.
The final quest rewards you with:
Along the way you garner about 1300 Stormwind reputation and the corresponding reputation with the other Alliance factions.
-  The Defias Brotherhood
-  The Defias Brotherhood (2)
-  The Defias Brotherhood (3)
-  The Defias Brotherhood (4)
-  The Defias Brotherhood (5)
- [18G2] The Defias Brotherhood (6)
- [22D] The Defias Brotherhood (7)