The Aghoru Campaign was an Imperial Compliance action carried out by the then-loyal Thousand Sons and a small contingent of the Space Wolves Legion in the waning years of the Great Crusade, sometime in the early 31st Millennium. Though Imperial Compliance was successfully accomplished through diplomacy and considered a success, some notable combat action took place between the Thousand Sons and an apparent Warp denizen infestation (beings known to the local population as "Elohim") within the subterranean passages of a titanic peak known as "The Mountain") which the Space Wolves helped to put down.
The world of Aghoru was the fifth planet in a star system of otherwise Dead Worlds, discovered by the Thousand Sons' 28th Expeditionary Fleet at the height of the Great Crusade. Aghoru soon proved to be home to an underdeveloped culture of human inhabitants, also known as the Aghoru, who possessed little to no knowledge of science. The Imperial Compliance of Aghoru (officially codified in Imperial records as planet 28-16) was an action carried out by units of the Thousand Sons Legion that was achieved through diplomacy and was considered a success. Interestingly, the human population possessed ancient legends of a race of elder beings known as the "Elohim" (which might be analogous to the Eldar). According to their mythology, a perverted and corrupt daemonic force, known as the "Daiesthai," who had succumbed to the corruption of the Elohim's self-obsession and hedonistic excesses, was imprisoned within the massive, artificially-constructed peak, designated by the Thousand Sons as "The Mountain." This titanic peak was set in a salt plain at the edge of a valley and rose larger than the tallest peak of Olympus Mons on Mars. Surrounding the base of The Mountain were scattered circles of raised stones, designated as "deadstones," each rising taller than three men. These deadstones served as a tool to blunt the psychic forces surrounding the artificial peak.
The Thousand Sons Primarch Magnus the Red was enthralled by the planet's mountain and the tomb of the dormant Daiesthai. Upon further investigation within the artificial mountain, Magnus discovered that it was some kind of gateway with a web-like network of conceptual conduits, containing billions of pathways between worlds. Unfortunately, Aghoru's link to the network had become corrupted by the Warp and was ultimately sealed.
During the Thousand Sons' time on Aghoru, somehow Khalophis, a Captain of the Thousand Sons 6th Fellowship (Company), seemingly awoke the mysterious force when he struck the base of one of the mountain's guardian Titans (which resembled Eldar Titans, though this has not been explicitly confirmed). Roused from their millennia-long slumber by the corrupt force of The Mountain, the valley's guardian Titans awoke and began to attack. The Titans were only defeated through the combined efforts of the Crimson King, his Thousand Sons and a contingent of Space Wolves, who had recently arrived to support the campaign in the Ark Reach Cluster. In the battle's aftermath, Magnus explained that the Warp denizens they had encountered were, in reality, daemons, among the most dangerous of the inhabitants of the "Great Ocean".
- A Thousand Sons (Novel) by Graham McNeill