The Siege of Thrysus

"Cries of Zealotry finds itself bounding across the halls of hollow nihilism. No gods will save the Thyrsian people today- only flesh, and indefatigable purpose." -The Highwayman
Thrysus was a planet of the Thyrsian System, located in the Inner Rim of the galaxy. Homeworld of the mercenary Sun Guard, the planet and it's capital, Nicea, were at the heart of the people's Empire. This came to an abrupt and brutal end at the hands of the entities from The Otherside; a strange, distorted and twisted reality bleeding into our own.
A primordial, gargantuan entity of the Otherside, known only as the Mother Moon, suddenly eclipsed to main orbiting Sun of Thrysus, blotting out the sky and casting the shadow of a Solar Eclipse onto the planet's surface. In a mere hour, Admiral Konrad C. of the Republic Navy drove his fleet of three Acclamators-class and two Venator-class ships to defend the allied planet alongside the native forces.
The Moon then began to sink massive claw-like appendages into the second Sun, appearing to open up and "Consume" it whole. At this point, the Fleets began opening fire and offloading Fighters to intercept. After releasing the second Star, The Moon released strange, flesh-blighted fighters near-identical to that of the Thyrsian Fleet. After more mutated cruisers emerged from the singular gaping "Mouth" of the entity, it began to grapple above the capital of Thrysus, Nicea, the orbital collisions already disrupting the environment, twisting and distorting structures of the planet. Sandstorms and tsunamis of dust flooded nations and hundreds of cities, Nicea itself barely standing after the initial climate change. This singular move already put down 25% of the planet's population buried. At this point, the 512nd Clone Armor Battalion was deployed to combat the sights of on-planet threats and provide aid to the surviving population.
Two and a half hours the initial landing, The Moon began to blight the surface with mounds of mutated creatures from the Otherside, alongside what appeared to be Urali Forces including dropships, fleets, and soldiers mutated by the planet. And for the first time on Thrysus- it had rained. The airspace had begun losing ARC-170s like flies to a swatter, prompting the retreat of Republic Personnel, with three Acclamators entangled by the moon, and they and it's crew were bombarded by the Venators as a mercy killing by the Admiral. The 512nd, without support, were brutalized by the forces and left to the wayside. As the carnage died down, forces continued to wreak havoc on the survivors, a transmission by the 512nd Commander escaping the orbit into main, galactic space for all to hear- those of the Theatre recognized the call- and they must answer.
To be continued in Space Hulk: The Crimson Court...