Cadian Gate

The cadian gate is sanctioned outside imperial territory on a world called Cadia.

Purpose
The reason the gate was made was so Chaos could not flow into the galaxy and engulf the imperium. It is held by the Imperial Guard Cadian armies.

History
The chaos lord Abaddon the Despoiler is the only chaos lord to Date to gain a foothold on the gate after The 13th Black Crusade in which Minor chaos victories resulted in capture of a small imperial settlement.