The story of Silithus.
Silithus is a sun-blasted desert in the far south-west corner of Kalimdor, reached only through the jungle of Un'Goro Crater. It looks empty, but beneath its sands lies one of the oldest evils on Azeroth.
This is the land of Ahn'Qiraj, a remnant of the ancient Aqiri empire. Its rulers, the insectoid Qiraji, serve the Old God C'Thun, and their swarming silithid servants once spread across the south of the continent. A thousand years ago, in the War of the Shifting Sands, the night elves and the dragonflights drove them back and sealed them behind the Scarab Wall. The seal held for centuries, but the hives are stirring again; silithid have pushed out into Feralas and Tanaris, and the desert crawls with them.
The Cenarion Circle keeps watch from Cenarion Hold, the only real settlement in Silithus, studying the hives and gathering the strength to face what waits behind the wall. They are not the only ones here: the Twilight's Hammer cult has camps in the desert and serves dark masters of its own, and elemental lords have sent their servants to the surface. Among the dunes lie the ruins of Southwind Village, a reminder that people once tried to live here.
Written for this site from the game's lore. Further reading: Silithus on Warcraft Wiki.

