The Black Lions were sent into the fray in the nearby system of Hades LXIV, one of many systems with similar names given their proximity to the Eye. The Chaos overlords had made an outpost of it, capable of striking easily at Invictus, as well as any of the worlds the lay behind its protection. Its continued existence was not to be tolerated by the Militarum, but so far the assaults to eradicate Chaos’ presence on the only habitable planet in the system had yielded little but a steady flow of notifications to families of the fallen.
But it was them or us. The war had to continue.
Planetary conflict on this scale is a question of combined arms and the careful measure of aerial superiority and careful siege warfare. The defender in this case, Chaos, had every advantage, being firmly entrenched within the rocky planet surface and sending constant reinforcements from the Eye into the air and space above.