Imperium react to Chaos at Tarlius

Finally, by early 12.017M42 the Imperium realised that the forces of Chaos were not in fact raiding the Tarlius system, but a full scale invasion was underway. Tarlius had a small population, but its position meant it was now critical to securing of the Foramen Minoris - the main space lane between the Imperium and the Perseus Deeps. 

Warsmith Stahl had already created two fully operational bases on the outer planets of the Tarlius system, but seeing his succecss, the other chaos factions decided to lend their "support" to Stahl's campaign. Whether he liked it or not. The Emperor's Children and Thousand sons, led by Magnus himself, landed on Tarlius 3, a rocky cold desert world, intending to expand the influence of chaos to all habitable planets in the system. Creating bases and defences on all of them would render an invasion by the hated imperium much harder.

The Imperium reacted swiftly to the sudden escalation of the Chaos presence in the Tarlius system, sending a full battlegroup and Admiral Jellicoe's fleet. The fleet presence ensured that Stahl's warships did not intervene, while the Mechanicum sent their own forces from Vandrax, this time to aid the Imperium, as the Crusade also wanted to maintain control of the Foramen Minoris, rather than see its destruction.

The Imperial forces landed on Tarlius 3, but found Magnus's "Emerald Serpent" ready and waiting for them, while the Emperor's Children were ravaging the human settlements on the world. Cybixx took the fight to Magnus, while a division of loyalist Librian forces were set the task of hunting down the other traitor legionaries.

The Librians knew they could not hope to track down the Emperor's Children, so instead they set up defensive positions in settlements not yet raided. Sure enough the traitor astartes took the bait, walking into the crossfire of Librian gunfire. Initially the chaos marines found themselves in difficulties, as they lost their transports to withering heavy weapons fire and suffered significant casualties. The super human veteran fighters were not stunned for long however, and soon used the terrain and ruins of the settlement to advance on the Librian positions. Noise marines covered the imperial positions with gunfire inflicting massive casualties on any units caught in the open, before finally closing and dealing with the heavy armour in close combat.

The engagements occurred across the plains of Tarlius 3 for days, but each time the Emperor's Children were unable to break the imperial defences completely, while the Librians were unable to wipe out the chaos threat. A stalemate ensued, and the battle would be decided by the encounter between Cybixx and Magnus. The mechanicum however found themselves in difficulties, and after exchanging heavy fire with the Thousand sons, this time, unlike in other encounters, the Emerald Serpent was able to close with the Mechanicus positions and inflict heavy casualties. Cybixx, unable to respond adequately to the new aggressive tactics, was forced to withdraw, isolating the Librian defenders and making the Imperial hold on Tarlius 3 extremely tenuous by 0912.017M42.