Cadian System

The Cadian System is the star system of the Cadian Gate, the only fleet-scale corridor out of the Eye of Terror. It sits in the Cadian Sub-sector of the Cadian Sector in Segmentum Obscurus, and Cadia was the fortress world that named both the system and the Gate. Imperial warfleets used this corridor as the lock on the Eye for ten millennia, with Cadia's pylons keeping the local warp quiet enough for a fleet to pass.

When those pylons failed in the 13th Black Crusade, warp storm Baphomael swelled out to the system's edge and Cadia itself broke. Sister worlds in the same system took the remaining Chaos spearhead while the Great Exodus shifted Imperial defences off the dying fortress and onto those surviving worlds. Kasrs, forge-moons, and penal stations around the Gate became the new front rather than a rear dump for Cadian-born regiments.

Cadia is now a shattered daemon rock - later seized from a Black Legion garrison by Iron Warriors - but the Cadian System still matters as the Gate even though the planet that named it is gone. The corridor remains the one fleet-scale way out of the Eye, which is why the Imperium still fights over the wreckage of a system rather than abandoning the name.