Hive Fleet Gorgon was a Tyranid Hive Fleet which invaded the T'au Empire in 899.M41. The Gorgon was a splinter fleet of Hive Fleet Behemoth that had been founded by those Tyranids who had survived the Behemoth's destruction during the Battle of Macragge and which began consuming poorly defended Imperial worlds to replenish its small numbers. By the time this splinter fleet made its way into T'au space in the Eastern Fringe of the galaxy, it had grown to become a full Hive Fleet in its own right. Hive Fleet Gorgon was relatively small in size compared to the other Hive Fleets that assaulted the galaxy, but it was characterised by an extremely rapid rate of adaptation to new weapons and tactics that was astounding even for a species renowned for its ability to direct its own evolution to meet new challenges. In response to the pulse weaponry and long-ranged tactics of the T'au, the Gorgon's primary strategy was the utilisation of smaller and faster-breeding Tyranid organisms to accelerate its evolutionary process. As a consequence of this strategy, the larger Tyranid biomorphs were few in number within the swarms of the Gorgon. Hive Fleet Gorgon was finally destroyed in 903.M41 at the Battle of Worldspine Ridge on Kel'shan by the combined forces of the T'au Fire Caste and the Astra Militarum.
It is possible that this extremely rapid adaptability was an innate characteristic of the Tyranid strains that comprised Hive Fleet Gorgon. However, the truth may lie in the unusual nature of the Gorgon's foe. The T'au are no less dynamic a species than the Tyranids, always willing to adapt, though their methods are rooted in the flexibility of their technology rather than biological evolution. The T'au proved to be a very different kind of foe for the Tyranids, one less hidebound by tradition and doctrine than either the humans of the Imperium of Man or the Eldar of the Craftworlds. As such, Hive Fleet Gorgon may simply have had to adapt even faster to defeat this new kind of enemy.
As the war between the T'au and the Tyranids progressed across T'au space, both the invaders and the defenders rapidly adjusted to their opponent's tactical shifts. Both sides tested each other for a weakness that could be exploited whilst preventing their foe from doing likewise. The T'au Supreme Admiral, Kor'O'Vanan, soon realised that only a fluid strategy that combined the entrapment tactics of the T'au Fire Caste's ancient Kauyon disciplines with the aggression of the tactics of the Mont'ka could provide victory. But tactical difficulties were just the beginning of O'Vanan's troubles as the Tyranids moved to adapt not just to the T'au's tactics but to their weapons technology as well. In response to the T'au's Pulse Rifle technology, the Tyranids restructured their biomorphs' carapaces, dramatically increasing their resistance to the Tau's energy weapons. In response, the T'au reconfigured their weapons to use either new or even older versions of the weaponry that the Tyranids had not before encountered and therefore could not have adapted to. However, each time they faced the T'au in combat, the Tyranid Hive Mind adjusted its biomorphs' reproductive matrices to meet the challenge with new phenotypes.
During the Gorgon's initial assault on the forest world of Sha'draig, the ferocity of the Kroot Auxilia commanded by Shas'el Vorcah was decisive in repelling the Tyranids' first landings as the Kroot mercenaries proved more than capable of holding the swarms of Hormagaunts at bay. But the Hive Mind adapted and the second wave of Hormagaunts to assault the world were noticeably swifter than their predecessors, able to move through the planet's twisted foliage without fear of becoming entangled. Many thousands of Kroot gave their lives to stop this second invasion.
When the third invasion of Sha'draig inevitably began, the Hive Mind had altered the Hormagaunts further, increasing the efficiency of the creatures in tearing through the thick hide of the Kroot. Unfortunately, this third wave made quick work of the forest world's Kroot defenders, yet the genetic changes made to the Hormagaunt biomorph weakened the creatures' own resistance to injury as the Hive Mind had traded thicker carapaces for more powerful musculature and speed. This allowed the T'au, using the time bought by vast quantities of Kroot blood, to blow them apart with their powerful ranged energy weapons.
In the end, Hive Fleet Gorgon's extreme adaptability proved to be its chief vulnerability, as the rapid cycle of adaptation and replenishment of its forces forced the Tyranids to rely on their smaller, less complex biomorphs that could be bred most rapidly. The Gorgon had few of the larger and more potent Tyranid biomorphs at its disposal and those it did possess were not easy to replace. Once the T'au recognised this reality and made the elimination of these creatures a priority for the Fire Caste, the course of the war dramatically shifted in their favour.
The last weeks of the T'au Empire's campaign against Hive Fleet Gorgon unfolded on the Sept World of Kel'shan in 903.M41. Even as the Tyranids had threatened T'au space, the T'au of Kel'shan had already been involved in a war against the 18th Cadian Army of the Imperial Guard. Once the Tyranids entered the star system, the commander of the Cadian 18th, Castellan Crask, temporarily ended his battle with the T'au and joined with their forces to shatter the Hive Fleet that represented a danger to every living thing on Kel'shan. The truce lasted only until the last Hormagaunt was slain, but such was to be expected from the xenophobic forces of the Imperium of Man.
While the Gorgon had represented a terrible danger to the T'au Empire, by Imperial standards this splinter Hive Fleet had been only a minor irritant. Crask believed the T'au to be weaklings for having such difficulty in scouring such a small Tyranid force from their space since he did not realise how far the T'au had already degraded the threat by the time it reached Kel'shan. This misunderstanding of the situation was the primary factor in the commencement of the Imperium's Iron Hammer campaign against the T'au, which eventually escalated into the greatest confrontation seen yet between the Imperium and the T'au Empire.
Despite their victory, the invasion of T'au space by Hive Fleet Gorgon would leave a dark shadow upon the future of the T'au Empire. Just before the Gorgon's final destruction, three Hive Ships had broken off from the main fleet of bio-ships and headed back into the intergalactic void beyond the galactic rim with elements of the Tau Navy in close pursuit. These Hive Ships carried within their adaptive genomes the full scope of the Gorgon's experiences in battle with the T'au. The T'au mistakenly believed that this knowledge could only be transferred if these Hive Ships survived to make physical contact with other Tyranid Hive Fleets that were moving on T'au space. This was not the case, and the T'au were likely to face further incursions from the Great Devourer that would reveal the true scope of the Tyranid threat to all forms of life in the Milky Way Galaxy.
The Gorgon's Course
Assault on the Forest World Sha'draig
The T'au were first alerted to the arrival of Hive Fleet Gorgon within their space in 899.M41 when the worlds of several Imperial trading partners were consumed. Next, all contact was lost with the Outbound Brotherhood T'au explorer fleet after it strayed into the path of the ravenous Tyranids. The T'au fleet was consumed so quickly that not a single warning of the coming onslaught managed to escape.
It was in late 899.M41 that the forested colony world of Sha'draig's orbital system perimeter outpost was eliminated by a Tyranid assault. The Kel'shan Sept Fleet, under the command of Kor'O'Valroth, slipped its moorings and headed for Sha'draig.
In early 900.M41, the orbital shipyards on Sha'draig's moon were attacked by Hive Fleet Gorgon's outriders. With all other options ruled out, the defenders of the shipyards sealed themselves within their main complex, trusting to their interceptor screens to buy them time. Tens of thousands of Tyranid Gargoyles died under T'au interceptor fire. The Tyranids moved on to the forest world of Sha'draig, leaving only a handful of bio-ships to blockade the moon.
A new strain of Gargoyles then attacked Sha'draig's lunar complex. The interceptor screen opened fire once again, but the power of its strikes had been lessened by a new refractive mucous coating that now covered the Gargoyles' chitinous hides.Their primary means of defence lost, the Sha'draig lunar shipyards were finally overwhelmed.
By the time the Kel'shan Sept Fleet arrived at Sha'draig it found the world already under full siege by the Gorgon. The T'au fleet breached the Tyranid blockade of the forest world long enough that it was able to deliver Fire Caste reinforcements to the world's defenders but was forced to retreat from direct combat. Kor'O'Valroth ordered hit-and-run attacks to begin on the Hive Fleet's perimeter. With his defences bolstered by additional warriors from Kel'shan, Shas'el Vorcah sent his Kroot auxiliaries to create an outer defence line on the surface of Sha'draig that will meet the Tyranids' initial ground assault.
Late in 900.M41 a vast swarm of Tyranid Hormagaunts assaulted the Kroot defensive positions in the great forests of Sha'draig. Many of the invaders were entangled by the forest's heavy foliage and undergrowth or caught in the Kroot's specially-prepared traps. Under the command of Shaper Pechallai, the Kroot managed to drive the Tyranids back from the outer perimeter line.
Despite the defeat, in early 901.M41 Shaper Pechallai's position was assaulted once more, this time by a modified variant of Hormagaunts who had been bred swifter by the Hive Mind, and thus were less vulnerable to being ensnared by the forest world's undergrowth or Kroot traps. Only brute force and sheer tenacity allowed the Kroot defenders to hold the line this time. Unfortunately, a final wave of Hormagaunts, honed into their final phenotypical forms by the Hive Mind, swamped the carefully prepared Kroot defences of Shaper Pechallai. However, following their heavy losses to T'au Fire Warriors, the Hormagaunts and Termagants of the Gorgon developed an almost total immunity to the fire of T'au Pulse Rifles. The main settlement of Sha'draig was finally overrun by the Tyranids and Shas'el Vorcah chose to withdraw his remaining forces into the forest world's mountains.
Following this defeat, T'au Stealth Teams recovered several hundred Kroot rifles from the ruins of Shaper Pechallai's final defensive perimeter. This weaponry was dispersed amongst Sha'draig's remaining Fire Warriors. In orbit of the forest world, fresh broods of Hormagaunts and Gargoyles were spawned by the Hive Fleet wth chameleon-like hides that allowed them to completely blend in with their environment. They were now nearly invisible to the naked eye and only the sensor packages of Tau Battlesuits could be relied upon to accurately detect them.
Realising that the situation on Sha'draig was now untenable for his forces, Kor'O'Vanan ordered the T'au Fire Caste's withdrawal from the forest world and the Kel'shan Sept fleet broke the Tyranid blockade long enough to retrieve the bulk of the surviving T'au ground forces left on the colony planet. Shas'el Vorcah refused to abandon hope and he and his Hunter Cadre chose to remain on the world under the pretext of covering the T'au retreat but with the full intention of remaining behind to continue to fight despite the long odds.
In late 901.M41 Shas'el Vorcah initiated a series of suicide missions that shattered the Tyranids' web of Synapse creatures on Sha'draig. The success of this operation drove the Tyranids of the Gorgon from the forest world, but it proved a pyrrhic victory as Sha'draig has been almost completely consumed by Ripper Swarms. Vorcah's Hunter Cadre abandoned the near-lifeless planet not long after, taking some solace in the fact that they had denied the Tyranids the entire planet's bio-mass.
The Harvest of Ka'mais
In early 902.M41 dozens of Hive Ships separated from the main body of Hive Fleet Gorgon and descended upon the T'au colony of Ka'mais. Bitter fighting erupted as a fleet of Necron starships unexpectedly emerged from within Ka'mais' dead moon, which had been a secret Necron Tomb World, its undying inhabitants' long sleep disturbed by the conflict between the T'au and the Tyranids. The outnumbered Tyranid bio-ships were destroyed. This unexpected victory led to a day of celebration amongst the T'au on Ka'mais. Unfortunately, the Necrons landed a force on the colony world to be greeted in great ceremony by the honoured Ethereal Aun'taniel. The T'au had never encountered the Necrons before and thus did not realise that the undying machine race represented a threat as great, if not more so, than the Tyranids. Aun'taniel was slain by the Necron invaders, who immediately began harvesting all of the T'au on Ka'mais for their C'tan Star Gods. In response, the Kel'shan Sept's Ethereal Council ordered the evacuation of the remaining T'au colony worlds that lay between Ka'mais and Kel'shan.
During the evacuation of the colony planet of Ho'sarn, the fleet was ambushed by Tyranid Prowler drone bio-ships. More than 300 T'au vessels were lost to the Gorgon in less than 3 hours. A small group of T'au ships escaped to the abandoned mining facilities on the edge of the Ho'sarn System. The survivors tried to fortify the decrepit residential buildings of the mines, but the improvised defences were easily swept away by the Tyranids that arrived on the planet 2 days later. Not a single T'au survived the Massacre of Ho'sarn.
In mid-902.M41 the T'au engaged Hive Fleet Gorgon in the Battle of the Sol'ai Rift. Kor'O'Vanan's fleet engaged the Gorgon as it left the Ka'mais System. The battle at first went well for the T'au Navy, but they were forced to retreat after encountering a cluster of Ramsmiter and Razorfiend bio-ships that had developed immunity to the T'au's ion weaponry. Before the T'au fleet withdrew, they did succeed in slaughtering many of the Gorgon's Narvhals, hoping to buy enough time to fortify Kel'shan against the Tyranid onslaught. Not long after the battle at the Sol'ai Rift, the world of Roksh, the home of the Rokshashi Wealthweb merchant guilds, was completely consumed by the Gorgon. Several T'au trading fleets were lost in the Roksh System, including a secret T'au Fire Caste listening post on Roksh XVI. Meanwhile, Valroth's fleet had returned to the Kel'shan Sept's orbital shipyards. The fleet underwent major retrofits in an attempt to overcome the Tyranids' recently developed immunities to ion fire.
Victory at Kel'shan
An Imperial Navy fleet, sent into the Warp more than 150 Terran years before to support the then on-going Damocles Gulf Crusade, arrived at Kel'shan unexpectedly in late 902.M41 after being trapped and delayed in an eddy in the Immaterium. Unaware that a Tyranid Hive Fleet was already assaulting the region, the fleet entered orbit of Kel'shan and besieged the planet. The commander of the 18th Cadian Army of the Imperial Guard that was carried aboard the fleet, Castellan Crask, led his Guardsmen in a planetary assault. Valroth's fleet, its modifications completed, left the orbital shipyards and immediately engaged the human besiegers. Not long after the Imperials arrived, the Tyranids entered the Kel'shan System and joined the already ongoing battle in orbit and on the planet below, initiating a short three-way conflict. But faced with a common enemy that represented a terrible danger to them both, Castellan Crask and Kor'O'Valroth agreed to an uneasy truce. Acting in concert, the Imperial and T'au fleets cut deep into the Gorgon's fleet of bio-ships. Tyranid casualties proved heavy, and almost all of the bio-ships were destroyed. In the confusion, 3 Hive Ships fled the star system. Kor'O'Vanan's T'au fleet pursued the Tyranids and fleet engaged the surviving Hive Ships at the Delmarra System. One of the Tyranid Hive Ships was destroyed but succeeded in luring the Kir'shasvre (Castellan)-class Fleet Carrier Firestar into Delmarra's asteroid belt where it was destroyed. Outnumbered and outgunned, the remaining bio-ships fled, drawing the T'au even further from Sept worlds that were now left unprotected.
In early 903.M41 the Cadian 18th Army and the Kel'shan Sept's Fire Warriors purged the remaining Tyranids from that world. With the destruction of their fleet, the Tyranids no longer possessed any reproductive capacity on Kel'shan save for a single Dominatrix and a group of already-battered Tervigons. That reality, and the combined tactics and different weapons of the T'au and Astra Militarum, now prevented the rapid adaptation that the units of Hive Fleet Gorgon had displayed in previous encounters. As a result, at the final Battle of Worldspine Ridge in mid-903.M41, the last Dominatrix and Hive Tyrant of Hive Fleet Gorgon were both slain by combined Imperial and T'au forces. Though the alliance between the Imperial Guard and the T'au promised to break down into renewed combat almost before the last Tyranid corpse had grown cold, the terrible threat of Hive Fleet Gorgon had been ended.
- Codex: Tyranids (5th Edition), pp.18-21