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.