Tyranid advances

The end of the Tau colony on Memnon came on 0702.014M42, just 4 months after the invasion by the orks and tyranids. The tau had taken refuge behind their last line of defence, their position ensuring that a last stand was inevitable. The tau forces knew their resistance was suicidal, as there was no prospect of their evacuation, but for the greater good a prolonged battle on Memnon was preferable to having Nemesis and the orks invade any more tau colonies.

First to appear was the Nemesis swarmlord, who appeared to be directing the horde of creatures which followed. The tyranids surged down one flank, attempting to bypass the tau manning a defence line, taking heavy casualties to the tau emplaced weaponry. Monsters were brought down by sheer weight of fire, but the alien swarm was resilient and seemed endless. Barrages of spores and finally a tunnelling Morlock circumvented the fixed tau defences, bringing close range death to the defenders. A desperate counter-attack by the tau commander and supporting Riptide into the heart of the tyranid horde was ripped appart by the swarmlord itself. The defences breached the surviving tau were forced back towards the sea, having had apparently no impact on the horde of bugs now swarming over their once peaceful colony. The tau hold on Memnon was over.

On Grimlock, the long war between the forces of Chaos and Nemesis continued, but while the swarm grew the defenders dwindled, and by 02.014M42 the shadow in the warp had completely obscurred the system from astropathic communication. Isolated, the defenders of Grimlock had to face the multiplyng hordes alone.

Having secured Atil late in 013M42, the hive mind knew it needed to push south, as the vital region of Repsis would be pivotal in deciding the outcome of the war. If the remaining chaos forces could be divided and surrounded, the war would be over much sooner. To this end the assault towards the chaos city of Tallin began in 02.014M42, with a major Tyranid advance. Defending the city, the mass of cultists were able to count on a small but critical number of Emperor's Children, who had vowed to stay and fight the alien menace for as long as it took to remove them from the sovereign world of their dark masters.

Nemesis however was nothing if not clever, and the swarm of tyranids surged forwards before the marines were fully prepared. Despite fielding a large number of astartes and supporting units, the chaos forces were unable to effectively concentrate their fire, and the protective psychic powers projected by the hive mind kept the alien swarm alive long enough for ravenors to reach the chaos lines. Bio-engineered for close melee actions, the ravenors quickly butchered any who stood in their way, millenia of service and enhanced human physiology offering little resistance to the perfectly adapted killing organisms.

The Emperor's Children launched a desperate reposte, sending in an ancient Land Raider Spartan and elite terminator warriors into the heart of the battle, where Nemesis looked like breaching the city's defences. However this small elite force was quickly overwhelmed by a mob of hormagaunts who, while posing little threat themselves, delayed the astartes warriors long enough for a Swarmlord to reach them and rip them apart. Eventually all that remained of the traitor astartes was the Spartan itself, which squashed the head of a Mawloc as it emerged from the ground, and then escaped to take word of the massacre to the city overlords.

The breach of the defences signalled the end of the defence of Tallin, and the chaos army fled in terror before the tyranid swarm. Repsis fell a week later and the tyranids were only held as the advance lost its momentum on the borders of Hakun and Orrin in the far south. the loss of either of these regions would seal the doom of all chaos forces east of the Errin sea, and hasten the end on Grimlock. In any case the loss of Repsis now sealed the noose ever tighter around the neck of the chaos dominion of the world.

Only in the Perseus Deeps did Nemesis continue to see reverses. While Memnon and Grimlock were being overrun, Bastien's cleansing was continuing. Having broken the back of the tyranid infestation the Carcharadons left, allowing General Veers to direct his own Guard forces to eradicate the remaining aliens. In early 02.014M42 a Corellian expedition to the northern mountainous region encountered several tyranid swarms, but the mechanised Imperial Guard units made short work of them. A large set piece battle took place on 1002.014M42, requiring the Corellians to commit their reserve, but after this action the alien resistance dwindled. Bastien would be considered free of the tyranid threat by the end of 02.014M42, although the threat from individual mindless tyranid creatures would remain indefinately.
 - Grimlock current