Into that Vast Expanse
The Cadian Gate is an area of calm space leading in and out of the Eye of Terror. It is located to the galactic south-east of the Eye, and is the only predictably stable way out. It is therefore a site of frequent raids by the forces of Chaos.
Several Black Crusades have emerged from here, including the most recent, the 13th led by Abaddon the Despoiler. This has led to its continuous monitoring and the stationing of several forces of Imperial Guard in the closest system, Cadia.