Prelude to the Starport Assault

The planet of Thrask was under the rule of the Imperium. Not that you'd be able to tell by casually looking. Due to its fairly small and innocuous size it was often overlooked. It had no vast deposits of materia to fulfil any imperial tithes. It's strength lay in its inhabitants. Although introduced to concepts of the wider Imperium, the lack of governance meant they remained much as they had been for centuries. This detachment made them ideal in o'Ralai's eyes for annexing into the ever expanding Tau Empire. With a little coercion they would make excellent Gue'vesa.

On board his Custodian class carrier and in conjunction with his ethereal council a plan was formed to make planet fall and introduce the local populace to the concept of the greater good. A concept he was sure they would embrace after being essentially ignored for so long by the oppressive humans.

Due to the lack of any real governance from the departmentus administorum, certain traits in the general populace of Thrask had gone unnoticed for generations. It was also a trait overlooked by the naive and some would say, ignorant, Tau. Psychic ability was rife, and also unchecked. On any other imperial world this would have been identified at an early stage, black ships would ferry back and forth, shipping the dangerous individuals to Terra where they would either be developed to serve the Imperium in life, or to be fed to the Astronomican to keep the Emperors guiding beacon shining.

It was this unchecked pool of psychic ability that had slowly been drawing the attention of the warp. Strange beings in the immaterial realm had taken notice and were hungry. Even if they all were devoured by the onslaught of the armies of Chaos, or twisted and enticed to forgo their souls to the chaos gods, it mattered not.

O'Ralai ordered the air caste in charge of his fleet to ready the Mantas, prepare the Orcas, and outfit the suits ready to make planet fall. As the sun set they launched their stealth invasion, the cover of darkness providing much needed cover. Although he was certain the Gue'la wouldn't have any anti-air capability he wasn't willing to take any risks. The landing site was a stretch of flatland surrounded by a crown of rocky outcrops and few miles to the west of the planets star port. Under advisement from his friend Aun'Li the subtle approach was chosen rather than just dropping the entire might of the Tau directly on top of the facility. The distance wouldn't pose any kind of inconvenience, the fast moving troops he was taking with him would cover the ground in no time at all.

As they disembarked from the huge transports and formed up into cadre groups the evening sky took on a sinister tinge. Out of nowhere clouds rolled in over the hills, and lightning erupted, closely followed by a thunder that raged harder and longer than the venerable commander had ever heard. At first he thought they had grossly underestimated the local population, and many of his cohort went to ground, taking up firing positions as the Piranhas and Tetras gunned they're engines and shot off into the distance to assess to situation. After a number of rai'kor that felt like an age, and no sign of any military retaliation, the order was given to resume advancing. The adverse weather conditions proved to be an unexpected ally, masking the noise of their propulsion systems as the advance party crested the hills surrounding their target. Little did they know that the Tau weren't the only beings interested in this vital piece of infrastructure.

As the star port and the surrounding landscape was revealed the fire caste halted for the second time within the hour. What they saw made no sense to their warp-neutral minds. The freak weather conditions were not coming from the sky, they were emanating from the fields almost directly on the opposite side of the port to them. Although thick fog and smoke billowed everywhere, and would've hindered the visuals of a less advanced race, the black sun filters of the tau easily pierced the smog and what they saw chilled them to the core.

Out of the swirling, tempestuous mists emerged myriad shapes. Some vaguely recognisable to o'Ralais hunter cadre as Astartes, others so alien and twisted they were beyond classification. Foul nightmare creatures apparated out of thin air, their hisses and cries carrying clearly over the stretch of space separating the two forces. Huge war constructs started their ponderous journey towards the outbuildings of the starport, and the Tau commander knew it wouldn't be human resistance to cause them trouble. Over internal comms he gave the final order, and the battle commenced...

(This is my first real attempt at creating a story, so please excuse my amateur ramblings!)