@supertinykingBillions of ships set out, facing the seemingly tiny fleet of Chaos, even as it had split up it's fighting force. And yet they were impossible to hunt down. Guided by the Dark Gods, they simply warped out and into this reality at will. Twenty different planets found themselves suddenly under attack, as five ships appeared in orbit. The ships that had been sent out to meet the invasion force were completely left behind, only to port in behind the Chaos ships. They witnessed that each of the twenty detachments was identical. Each consisted of a single massive battleship, and four lighter frigates. Each of these ships was massive, painted a rusted, greenish bronze. Covered in massive seemingly pointless spikes, writing tendrils, and surrounded by a cloud of daemonic beings. Great pestilent clouds seemed to whirl around the ships, as the Dominion forces confronted the malicious power of the Warp.
On each location the Chaos ships were outnumbered a thousand to one. It seemed like it would be over in mere moments, as the Dominion ships prepared to fire. And yet, even as they locked on their weapons, no order to fire ever came.
A Chaos Marine in Terminator Armor appeared in the command room of one of the ships, easily resisting the small arms fire as it tore through the commanding officers. Another ship found itself filled with Plaguebearers, or Infection Savants, as the soldiers of the Dominion claw out their own eyes and throats. Horrific plagues spread through the fleet, each species finding a plague handcrafted for them. Those lucky enough to find hazard gear were merely slaughtered by the Plague Marines, Cultists, Plague Savants and Plaguebearers. With the aid of these plagues, against which the Dominion had no defence, and their capability to warp into enemy ships, the Chaos forces decimated the Dominion fleets. Entire ships were filled with the screams of the damned, as the plagues of Nurgle stripped the skin from their bones, killing them only after hours of agony. The Apostles of Contagion had come, a full chapter of Chaos Space Marines, seperating themselves into twenty armies of 50 marines, each backed up by 100 daemon and 500 lesser beasts, among which are cultists and mutants. Casualties for Chaos were minimal.
During the fighting, canisters were dropped from high orbit into the hive worlds below. Not the drop pods usually employed by the Chaos Marines, but rather specialized biochemical weaponry. They seperated in high orbit, before spreading gas across the planet's surface. Warp-infused virusses spread through the planet's atosphere, infecting most intelligent beings on the planet. While the initial effects could not be noticed, soon they would find themselves facing a plague the likes of which this universe had never known.
19 Hive Worlds would thus fall. But for one, it's fate was different. For even as the creatures of the Warp engaged in their orbital battle, the One would observe from below. It would be able to interfere, and perhaps save this lone world. However, even it's power was limited by it's location. And it could only do so much. Above, already, the dominion forces were succumbing to Nurgle's crafts, and several canisters had been dropped into the atmosphere, ready to release their load.