The Relief of Stonekraal was an Imperial military campaign conducted by the Exorcists Space Marine Chapter in defence of the Frontier World of Stonekraal from the predations of the Tyranids of Hive Fleet Behemoth in 740.M41. The Behemoth was the first Tyranid Hive Fleet encountered by the Imperium of Man, and also represented the first contact the Imperium had with the Tyranids as a race. Before the full extent of the Tyranid threat was realised, Hive Fleet Behemoth would slash a murderous wound deep into the Imperium before being halted at the Battle of Macragge in 745.M41. In the years prior to this outcome, as the Ultramarines fell back to their Chapter world, much of the defence of the Realm of Ultramar was left in tatters and helplessly exposed before the hunger of the Great Devourer. Many worlds fell, their cries for aid unheard or ignored, while a scant few were fortunate enough to escape by blind fortune or outside help. The bleak and often overlooked minor Frontier World of Stonekraal, located on the northeastern edge of Ultramar, was one such world.
In 740.M41, a scheduled trader vessel, the Nostros Vex, appeared three weeks overdue and drifting, seemingly lifeless, on the edge of the Stonekraal System, and it was investigated by vessels sent out from the small Imperial colony in the system. This heralded the beginning of a nightmare for the colonists of Stonekraal. Soon a rapidly multiplying infestation of Hive Fleet Behemoth Genestealers broke out, and in an ever-growing plague, the horrific creatures hacked through the scattered, hardscrabble settlements of Stonekrall like a butcher's cleaver through raw meat. Alone, and realising their astropathic distress calls were unlikely to be answered, the remaining Stonekraal colonists did their best to gather their few weapons together and mount a defence, determined to sell their lives dearly if they could. When all seemed lost and only the last major settlements remained, all that was left was for the terrified men and women cowering behind futile barricades to pray for deliverance to the God-Emperor. Yet that deliverance came as deep crimson Thunderhawk gunships descended on plumes of fire above them. The Exorcists Space Marine Chapter's 3rd Company, driven off-course by the Tyranids' psychic shadow in the Warp, had heard the colony's cries for help. Their Strike Cruiser Hand of Glory, having already slain two encroaching Void Kraken in the outer system, now off-loaded its complement of Space Marines to make a stand on Stonekraal's broken ground.
The battles that followed were swift but furious; the Genestealers first seeking to infiltrate by stealth only to be met by the firepower of the Exorcists Astartes waiting for them. The Tyranid broods quickly shifted tactics and sought to overwhelm their foes in a whirlwind of fang and claw. Inured as they were to the terrors of the Warp, even these nightmarish xenos, although deadly beyond measure, held little fear for the Exorcists Space Marines. With near clinical efficiency the Space Marines set up interlocking fields of fire to trap their attackers into pre-prepared killing zones in order to blunt the Genestealers' advantage in speed and numbers. Meanwhile the Exorcists' potent Librarian, Castor Machen, sought out the synapse creatures present within the brood and scourged them to ashes with coruscating soulfire.
The people of Stonekraal survived thanks to the Exorcists' efforts; a small victory, perhaps, in the grand scheme of the greater battle against the Hive Fleets, but a victory nonetheless. After-action testimony taken by Ordo Xenos investigators record the fearful awe the surviving colonists felt for their saviours, and many spoke of how the sound of the baleful litanies the Exorists chanted during battle still echoed in their dreams.
- Imperial Armour Volume Ten - The Badab War - Part Two, p. 127