Nethergarde Keep is a heavily defended Alliance town in the Blasted Lands. Though technically it's just a castle like Northwatch Hold in the Barrens, none of the Guards are PvP-enabled except the Gryphon Master.
Nethergarde Keep is a dam holding back the evils of a blighted land. It was built by the Archmage Khadgar, who led an expedition into Draenor long ago and was lost. The mages who occupy it today serve in honor of his memory. This medium-sized keep sits at the very north of the Blasted Lands, guarding the sole road into the region. Its mages and warriors have given up fun for duty and a constant struggle against demons and ogres. Some may think they are losing, but they continue to fight to protect the portal and the rest of Azeroth from Lord Kazzak’s forces. However, the Keep’s greatest problem is not the threat from the outside but the apparent threat from inside. Thas’ranan and Lordenson share leadership, the first leading the mages and the second the warriors. They are rarely at odds, but when they are, the other inhabitants make themselves scarce as the sparks fly. The Keep’s people are a solitary bunch under a great deal of stress. The only building for miles, the Keep stands stark and alone by the road. Warriors man the walls at all times, watching for movement to welcome ambassadors or food trains from Stormwind, to turn back travelers, or to mount a defense against ogres or demons.
Nethergarde was erected just after the end of the Second War by Archmage Khadgar of the Kirin Tor. Its purpose was to monitor the Dark Portal and ensure that it never threatened Azeroth again. The Dark Portal was eventually closed for good thanks to the sacrifice of Khadgar and the Alliance Expeditionary Force, but Nethergarde Keep remained in operation. The wizards of the Kirin Tor became interested in studying the Blasted Lands due to the strange effect the residual magic of the portal was having on the local wildlife. During the invasion of the Burning Legion, Dalaran itself was destroyed. Now, with most of the remaining Archmages sealed behind the Dalaran force shield, Nethergarde is the only center of Dalaran's former power. It still depends on Stormwind for supplies, and welcomes Alliance warriors within its walls.
With re-entry into the re-discovered Outland imminent, it is likely that Nethergarde will become the Alliance's major hub of activity between Stormwind and the Dark Portal.