The Eye of Terror is a vast and malignant region of space where the material universe and the immaterial realm of the warp have merged into a single nightmarish expanse. Visible even to the naked eye as a lurid wound across the heavens, it is the largest such rift in the galaxy and the greatest stronghold of Chaos in the material realm.
Within its boundaries the laws of reality break down. Time flows unevenly, geography shifts without warning, and daemons walk freely alongside the mortals who serve the Dark Gods. It is here that many warbands of Chaos Space Marines make their lairs, dwelling upon daemon worlds and crumbling fortress-planets from which they launch raids into Imperial space. Whole civilizations exist inside the Eye, twisted and immortal, ruled by ancient champions who have bargained their souls for power.
The region was born of a cataclysm in the ancient past, an event tied to the fall of an elder civilization, and it has festered ever since. For the Imperium it is a permanent threat, ringed by fortress worlds and watched with dread, for from its depths pour the Black Crusades that periodically ravage the surrounding stars. The Eye is at once a hell, a haven, and a gateway between worlds.