Arx Mercatus

Arx Mercatus was once one of the major strongholds along a very rich Imperial trade route. The Imperial armies ruled it for centuries. The Emperor valued its use and saw that Arx Mercatus was watched over by the soldiers of the Adeptus Astartes, and led by a trusted commander, Librarian Hernnahan of the Dark Angels.

The evils of Chaos were always at work, looking for ways to dethrone the false Emperor. The Blood God Khorne was alerted to the importance of the stronghold. Khorne wished to ruin the Emperor and cut off all trade through this route. He sent troops of Bloodletters and Possessed Space Marines in to destroy Arx Mercatus.

The battle raged on for a decade. Although the bodies of many soldiers from either side were destroyed, the stronghold still stood. Librarian Hernnahan was able to empower his troops to hold their position and maintain the Stronghold. It took all of Hernnahan's power to do so, and in the end it was his undoing. Somehow, among the fighting, a lone assassin had crept into the main fortress. Stabbing Hernnahan in the back and killing him in an instant, the assassin fled with his mission successful. In one final push to overthrow the Imperial forces, the daemons of Chaos triumphed.

So strong was the Emperor's Touch on the the mind of this Librarian that when Hernnahan's mortal body was destroyed by the assassin, his psychic essence was melded to the Stronghold itself.

Khorne's mission was successful. He stopped the trade route and set up a Chaos base in his honor. Despite the efforts of the Chaos legion, they could not rest easy within the walls of the newly named Khorne's Keep. Eventually, the keep was abandoned all together. Khorne announcing that his mission was over and he no longer needed the stronghold. The Legion itself would never mention the real reason they left.