Shaehol is a Forge World of the Adeptus Mechanicus. Located in the dreaded Mandrigora Sub-sector, Shaehol had been cut off by a pall of vicious Warp Storms for many Terran centuries, until they finally abated and the Imperium launched the Second Aegisine Crusade in 633.M39 to reclaim the worlds of this sector. The Red Scorpions Space Marine Chapter was granted the honour of leading the assault on the rebellious Forge World, which had been taken over by a sect of Heretek Magi. The Red Scorpions successfully reclaimed Shaehol and brought it back into the Imperial fold.
Much of the early history of Shaehol has been lost to the mists of time, but at some point in the 39th Millennium, this once vibrant and productive Forge World had been cut off by a pall of Warp Storms and was lost for centuries. When the Warp Storms finally abated, the Imperium declared a Crusade in 633.M39 to reclaim the worlds of dread Mandragora. The Red Scorpions would gain high honour for their role in the later phases of the Crusade which re-conquered the worlds around the former sub-sector capital of Hecuba. These worlds had fallen under the tyranny of a heretical Mechanicus sect based on the once-proud Forge World of Shaehol. It was now a fetid world of chemical swamps and treacherous ash-wastes, its ecosystem wrecked by millennia of unrestrained industry. Shaehol was heavily defended by legions of insane, half-mechanoid servants loyal only to the Dark Magi who had created them. The paranoia of Shaehol's corrupt masters had invested the planet with innumerable layered defences made up of thousands of kilometres of living razor wire, clusters of hurricane mines and protected by labyrinthine fortress-mazes.
The Red Scorpions spearheaded the orbital assault against Shaehol, conducting a concentrated attack by Drop Pod assault supported by Thunderhawks and Caestus Assault Rams which managed to force a beachhead on the heavily defended planet. For 19 murderous solar hours the Chapter was forced to defend the landing zone against phalanxes of corrupted Combat Servitors, waves of surgically mutilated labour helots and the vast and baleful war machines of Shaehol, but they would not break. Only through the Red Scorpions' resolute action did they enable the Battle Titans of the Legio Tempestor and the Knights of House Vymar to safely land on the surface and deploy, then push past their valiant protectors to take the war to the foe.
It would take a further two standard years to fully re-conquer the fallen Forge World as the warped masters of Shaehol and their works were destroyed root and branch, but the Adeptus Mechanicus did not forget the Chapter's sacrifice. When at last the conquest was over and the Red Scorpions took their leave of the planet, the Mechanicus lords of war did them homage, as towering Knights and Titans lined the route taken by the Red Scorpions as they marched to the landing zones, bowing to them in homage as they passed by.
- Deathwatch: Honour the Chapter (RPG), pg. 35
- Imperial Armour Volume Nine - The Badab War - Part One, pg. 84