This quest is no longer available within the game.
Check your map to find an area under Scourge attack. Go there and damage a necropolis by defeating the Scourge around them. Return 10 of their Necrotic Runes to Commander Thomas Helleran at Light's Hope Chapel in the Eastern Plaguelands.
The floating necropolises of the Scourge plague the lands of Horde and Alliance alike. Tanaris, the Blasted Lands, Winterspring and the Burning Steppes are blanketed in the shadows of the flying fortresses.
Only through our combined efforts will they be repelled.
Each necropolis is supported by nearby magical circles, and among each circle swarms a host of undead creartures. We have determined that destroying these mindless hordes will destroy the circle's defenses.