In 10.022M42 the strategic situation in the Rifts of Hecate began to change as all factions realised the importance of securing Haven and Ergura's Fall to either control or close the Hecate Gap. Initial scouting began in early 10.022M42 as the Tau started sending pathfinder and stealth teams to Haven. One of these scouting teams was met by a squad of Sky Lords astartes performing the same mission for the Imperium. The brief skirmish was violent and dramatic, with the Tau stealth team displaying excellent marksmanship. This led to the decision by the Sky Lords to charge their enemy, and they narrowly managed to force the Tau to flee once they had closed the distance through withering fire.
At the same time a larger force of Iron Hands found itself facing off against a much larger force of Necrons. Defeat seemed likely, but the arrival of the eldar ensured the Necrons were forced to abandon their mission. This was not without its difficulties however, as the astartes and eldar also exchanged fire and interfered with one another's aims. This was no "alliance". The eldar desperately wanted to ensure the Necrons did not find the location of the Nexus Arrangement, the device holding open the Hecate Gap, but at the same time they didn't want the Iron Hands to achieve an absolute victory. No negotiations or pleasantries were exchanged after the engagement, and the eldar withdrew to the coastal strip of the main continent, building a base there for further interventions.
The Imperium continued to build a base around the necron tomb complex in the centre of Haven's barren but habitable main continent, amonst the ruins of a long dead civilisation. Further north however, the Imperial Guard were scouting the area for the construction of a second base. On 1510.022M42 it became obvious this would be more challenging than first thought, as they encountered the first elements of the tyranid threat, confirming inquisition reports that the hive fleet or fleets within the Rifts had discerned the imperial plan and were now seeking to gain control over the Gap itself.
The battle against the tyranids resulted in heavy defeat for the Imperium, and the remaining Guard units fell back to the imperial base in the south. Now the Eldar, Tyranids and Imperium had established themselves on Haven, and the battle for the Hecate Gap had begun in earnest.