Having rid the surface of Hexis of chaos forces and pushed back the tyranid and ork threats from Konev's base of operations north of the city of Praxis, continuing reinforcements and the increasing importance of having a secure base of operations in the lower Hadron Expanse, put a renewed focus on the securing of the world for the Imperium of Mankind. This impetus was further aided by the disappearance of the daemon-moon of Fecus Major from the skies of the planet. If Hexis could be completely secured, then a facility of operations could be constructed, a large amount of troops and equipment could be freed up to be used elsewhere, and the Adeptus Mechanicus would be free to explore the tomb complexes without fear of being disrupted.
the main threats left on Hexis were xenos. the orks still occupied much of Menthoteph, the tyranids infested the northern hills and to the south, the necrons posed an obstacle to securing the city of Praxis itself. The necrons were made up of a number of factions which did not have the same aims, but this was unknown to the Imperium who drew up battle plans to sweep out of their territory sector and force an engagement with the three xenos enemies. As it turned out, the centre of the resistance occurred as the imperial forces drove north and west from their front lines in Menthoteph, led by astartes and House Stroganov knights, the imperial guard followed closely behind giving strong fire support to the Imperium's elite elements.
The main decisive engagement in this imperial offensive took place in between the cities of Praxis and Menthoteph in a place known as "Old Town". General Konev's main offensive had been to use General Andreyevich's 3rd army that was based in the Great Sand Sea, rather than advancing from the more predictable direction - Ivanovich's 1st army in the north, which was still recovering from the battles against chaos. This new offensive put the tyranids on the imperial right flank, which met endless swarms of the smaller creatures and struggled to progress. On the let flank, House Stroganov charged into the orks holding south Menthoteph, immediately encountering the Bloodfang orks' most dangerous foe a hulking, clanking giant "Stompa".
The Imperial Fists chapter led the central assault, through the ruins of the city of Praxis and straight into the heart of the necron counter attack that was by now developing to counter the imperial move. A ruined mining complex separated the tyranids on the right from the orks and necrons, so general Konev had the advantage. His forces were connected and working together, while his enemies' were not. The orks and necrons allied in opposing the imperial advance, but the tyranids worked to their own agenda, and for a time successfully held off the imperial drive north. In the centre and on the left flank, imperial guardsmen were surprisingly effective in their bayonet charges against the soulless necrons, and the Imperial Fists became an immovable fortress, centred on a Spartan tank, that was the fulcrum about which the imperial assault now hinged. The charge of House Stroganov had been costly, as they lost an entire phallanx of mighty war engines, but it had been effective. The orks had been checked, their enthusiasm for the fight not diminished, but their ability to pose a threat to the imperial offensive now definitely was.
The necrons also faced their own problems. The warriors and vehicles which turned up were not from the Skareth dynasty. The lords of the Library of Silence did not see the point of wasting great resources on a pitched battle, and preferred to "await developments". Those necron forces that did take part in the battle seemed to be suffering from the ill effects of recent re-animation, as time and again shots were missed and fire was generally inaccurate. This cost them dearly and over the course of 10-15.021M42 the xenos forces were overrun. The orks were cleared out first, then the necrons were completely pushed out of the city. The tyranids took a lot of effort to hold, but once the orks and necrons had been sufficiently dealt with, Konev launched a second assault, declaring the planet "clean" of tyranid infestation some weeks later.
By late 12.021M42 the Imperium had fully secured Hexis, at least sufficiently to now proceed with the creation of a base, space port and various installations in the Lysis system to act as a jumping off point for wars in the Hadron Expanse. After many years fighting over the devastated ruined planet, Hexis was now in imperial hands... almost. Although the Imperium considered the planet now theirs, the Skareth Dynasty still had their own plans and both they and the eldar knew of webway portals the Imperium did not. Yes the Imperium could build a base, there was no question now of conquering the planet, but the fight under the surface for the riches of the necron tombs was far from over.