As both forces advanced on the outer buildings of their target, the starport, o'Ralai could see through the dense foliage that these were not the standard Astartes warriors he was used to facing. Where normal space marines appeared unblemished and straightforward, these were horrific to behold. Adorned with spikes, horns protruding from their armour, swirling sigils decorating their battle plate. These were an unknown quantity to him, and so the order was given to hold back and maintain a suitable distance until their style of warfare could be ascertained.
The forces of Chaos had no such reservations, advancing as far as they could up the battlefield. Huge war machines, half mechanical, half something else lumbered along besides the warped marines. Smaller infantry also accompanied them, a tainted mirror of the Tau's gue'la. These immense monstrosities opened fire almost as soon as they were within range of the Tau however the distance proved too great for the reaper autocannons to find their mark.
In retaliation, the hammerhead commander ordered the use of the rail cannon mounted on his hull. A blinding light streaked across the battlefield towards the scuttling human cultists, but despite the clearly superior technology the shot failed to make the first kill. Not willing to lose the initiative while the chaos marines advanced, o'Ralai led by example and fired a high density sabot shot from his experimental submunitions rifle, targeting the Dreadnought. It looked like a pale imitation of their own battle suits, without any of the grace and speed. The shot connected, finding a weak spot in the armoured bulk and detonated. The resulting explosion could clearly be seen from across the battlefield and the nearby chaos marines were caught in the fire. Only one of them failed to clear the area in time, his scream echoing among the port buildings.
Buoyed by his cadres good fortune the Commander ordered the Piranha to advance to a position just in front of the Defiler. Surely it's nose mounted fusion blaster would be able to decimate the construct. Sadly no weak points presented themselves this time and the opportunity was squandered. In retaliation the Defiler let rip with its reaper autocannon once again but the combination of the fast skimmers blinding pace and its disruption pods made it a slippery target and the volley of fire went wide.
On the far side of the battlefield the warped Astartes saw that the XV9s had over reached themselves, jet packing too far away from the bulk of the blue skins. They opened up with heavy bolter and plasma, crippling one of the agile suits and leaving them shaken. This was all the window of opportunity the great winged Daemon Prince needed. He made his move swooping down in a vicious vector strike, and despite the quickly aimed reactionary shots he feasted on the Tau in his clutches, tearing their exo-armour limb from limb, and then mimicking the same ferocity when dealing with the pilots. The Defiler, filled with rage from his failure to even dent the puny skimmer lurched forwards, it's many legs propelling it into the vehicle, wrecking it and leaving it a mangled pile of metal and blood in its wake.
O'Ralai knew that a few early casualties would occur, they needed to understand the capabilities of their new foe, and he knew that their lives had not been in vain, they had given theirs to further the greater good. From his vantage point close to the landing platforms he was able to coordinate a fast paced retaliation. Calling upon an elite unit of XV8 Crisis Suits to deep strike onto the field of battle. The raging warp storms surrounding the planet affected their accuracy and they scattered, not too far but just enough to keep them from being a threat immediately.
The next stage of the plan was for the two teams of Fire Warriors to take the twin skyshield landing pads. In their nimble Devilfish transports they made light work of the task, opening fire as they disembarked, catching a Cultist and a handful of Possessed in their torrent of pulse fire. Nearby, a cluster of Kroot were being shepherded into action by one of Aun'Li's ethereal cohort, and driven by his inspiring words recklessly fired at the demon prince to avenge the deaths of the hazard suit pilots. The hovering demon easily avoided the volley of fire, and the rounds that did hit were deflected by the armour covering his torso. He laughed at their ridiculous attempt to harm him with such inferior weaponry.
The three Tau crisis team, composed and alert after their rough deep strike found their bearings and sighted a unit of Chosen close by. Taking up firing positions they launched a furious torrent of ballistics and energy beams, scything three of the enemy down in one fell swoop. The Chaos gods, not wanting to be outdone by these young upstarts summoned an entity from the warp, one they believed would annihilate all in its path, but with so much action occurring in such a confined space as the starport the ghostly Obliterator failed to fully materialise. Sensing the commotion in the immaterium the demon prince knew that his masters were observing. His laugh turned to a hideous scream as he flew towards the Tau commander. He wasn't going to let those pesky bird men distract him from slaying the enemy warlord. He'd leave that for the Rhino advancing at full power towards them.
The airborne assault was unrelenting and vicious, the only thing saving o'Ralai was his accompanying marker drones, forgoing their standard priority to skim into the path of the demon's attacks, being utterly destroyed but serving their purpose by sparing the commanders life. On the other side of the landing field the Possessed, emboldened by the bravado of their leader charged head first into the Fire Warriors huddled around their transport. Two of the fire caste were mortally wounded, bleeding out on the hard metal plating. At the sight of such close up violence the remaining warriors fled to regroup and compose themselves. They weren't counting on the demonic fury of their assailants and all were bloody corpses in mere seconds.
Moments too late a further unit of XV8 Crisis Suits landed atop the skyshield from orbit, and although they were equipped to tackle heavy armour efficiently, they gave it their all to avenge their fallen comrades. Fusion bursts tearing Cultists and Possessed apart until only a handful remained. The Hammerhead pilot, ignoring his previous bad form during this engagement switched his targeting priority to support his commander, but due to evasive flying the Prince remained unscathed. He admonished himself and made a mental note that when this was over he would request a change of position, so that a better pilot than he might serve the greater good to better effect.
The opposite landing pad was a blaze of gun fire, the lone remaining squad of Fire Warriors cutting down the Chaos marine unit in front of them to around half size, no doubt inspired to greatness by the presence of the nearby Ethereal. Just below, the XV8 engaged the hulking, tentacled Maulerfiend, causing grievous damage but failing to put the demon engine down completely. The battle was in flux, and while both sides believed they would emerge victorious, neither sides belief was being backed up by battlefield practical.
The landing platform to the far right of the complex was a bloodbath. The Fire Warriors, backed by their suit-clad comrades engaged in deadly combat with a plethora of different Chaos monstrosities. Slowly but surely they were emerging victorious. The Possessed and majority of the Cultists being torn up by their superior fire power. The few remaining humans fled for their lives, not quite ready to give up their souls to the unseen gods of Chaos.
The sister platform held a very different story. An Obliterator finally emerged from the warp with no interference this time, and along with the Chaos marines began to whittle away at the fire caste who were attempting to hold onto the strategic asset. Just below, the wounded Maulerfiend lashed out at the closest thing to it, it's many limbs and whips making short work of the Devilfish transport, silencing its burst cannon once and for all. On the ground opposite them the Demon Prince moved in for the kill. He'd had enough of these stubborn blue aliens and instinctively knew he had to take out their leader to weaken the others. He swooped directly towards o'Ralai who was droneless and isolated. His fury was immeasurable and he hacked and slashed at the armoured suit. He bellowed a mighty roar as he finally penetrated the advanced alloys, utterly wrecking the commanders systems and forcing him to eject and escape the battlefield. The Ethereal and the mob of Kroot nearby, incensed by the fall of their mighty leader turned and opened fire. Maybe it was because the Daemons mind was clouded by the bloodletting, but he failed to avoid the volleys of fire coming from the Kroot rifles. They tore through his power armour and deep into his demonic flesh. The howls and screams of the vile beast eclipsing all other noises on the battlefield. A huge rent opened in real space, into which the demon was pulled, back to the immaterium from where it was spawned.
Now with both warlords out of action, both sides lacked the focus they needed to secure the objective. The lone Chosen marine did his best to control the bastion by sheltering inside. With no way to target him, the nearby XV8 team leveled their weapons at the building. They were equipped to take on heavily mechanised foes, and the bastion crumbled and burst apart like an egg being struck by a hammer.
The Maulerfiend and Defiler went into a rage, slaughtering everything in their path, Crisis suits and Devilfish becoming smouldering wrecks in the onslaught, but the forces of Chaos were no longer in control of the starport. Somewhere in the great beyond, the malevolent gods saw, and were outraged. As quickly as the tainted horde had materialised on the planet, they were apperated away, to receive the judgement and the furious vengeance that would be struck down upon them for their failure.
The Tau, wounded and severely in need of reinforcements were stunned. They had no idea what had just happened, and it took a moment for the battle-weary Ethereal to regain his senses enough to order the regrouping of the scattered squads, begin recovering the prized tech scattered across the field of battle, and to order the recon units to begin the search for o'Ralai's escape system. They had pulled through but only just. He was certain they would not be left alone for long, so their work to bolster their grip on the starport would need to be speedy, and the ships surrounding the planet would need to drop reinforcements to the surface with as much haste as possible.