"The Tyranid swarm must not be viewed as a foe set to destroy us, but as a tool. Our challenge is to learn to use that tool, so that it may not be used against the Imperium, but rather to assist the Imperium in fulfilling our manifest destiny."
Inquisitor Evaine Cartier
Dagon Overlord

A Dagon Overlord of Hive Fleet Dagon leading a Tyranid assault.

Hive Fleet Dagon was the first major Tyranid incursion into the Jericho Reach region of the Ultima Segmentum. The Shadow in the Warp cast by the Tyranid Hive Mind within this volatile region of space first heralded the arrival of this new and terrible Hive Fleet in 812.M41. Communication between parts of the Achilus Crusade and the re-conquered regions of the Jericho Reach was lost without warning. Particularly affected was the Orpheus Salient of the Crusade that was lost to communication and access with the rest of the Reach behind the Hive Fleet's crawling Warp interference.

In 814.M41, the Deathwatch warship Thunder’s Word entered the Freya System to investigate the silence of an astropathic relay. It found no trace of the relay and indeed no trace of any life in the Freya System. Preparing to leave the system, the Thunder’s Word encountered two Tyranid drone ships. Its hull scored and pitted with acid and its magazines nearly exhausted, the Thunder’s Word arrived at Watch Fortress Erioch bringing news that the Tyranids had come to the Jericho Reach.

Deathwatch holding the line

A Deathwatch Kill-team holds the line against a massive Tyranid incursion by Hive Fleet Dagon.

The Tyranid Hive Fleet that is assaulting the Jericho Reach is officially designated by the Imperium as Hive Fleet Dagon and has been identified as the greatest extant threat to the Achilus Crusade underway in the region, and indeed to the lives of every living being in the Jericho Reach. The Space Marines of the Deathwatch remain fully engaged in facing this threat. Not much is known about the origins of Hive Fleet Dagon other than that it hails from the edge of the galactic rim, far to the galactic east like all of the Tyranid Hive Fleets that have been encountered to date. It is highly suspected by the Imperial savants of the Ordo Xenos that this particular Hive Fleet may be a splinter of the decimated Hive Fleet Behemoth, which was destroyed during the First Tyrannic War in 745.M41 by Imperial forces.

This new Hive Fleet brings many all-too-familiar horrors to the Jericho Reach. Alongside the familiar, however, come new and disturbing Tyranid variations, proving once again that as soon as the Imperium believes it understands the Tyranid, that hideous species changes and adapts once more. For the Jericho Reach, the arrival of the Great Devourer was a mighty hammer blow, catching the Achilus Crusade off-balance and forcing Imperial Commanders to scramble to face this new threat before too much ground was lost and too many worlds had fallen. Meeting the swarms head-on, millions died in those first desperate years after Dagon's arrival, and many planets could not be saved. They disappeared forever under a rising and bloody tide of razor-sharp claws and clacking mandibles.

Commanders and soldiers alike came to know the signs and character of the swarm, the nature of its beasts and the unique hunger it seemed to possess for the Jericho Reach, as if it had a special taste for that sector's worlds. They also noted how it adapted and changed with each world it consumed, each battle it won or lost. This kind of rapid adaptation had been observed in other Tyranid Hive Fleets but in Hive Fleet Dagon it seemed as if the fleet were aware of the pain and suffering it was inflicting and the terror in the hearts of the soldiers trying to stop it.

In the space of a few short standard years, this evolution and mutation within Dagon led to a number of unique bio-constructs and weapons never seen before by Imperial xenos-scholars; the most terrible of them all being the Dagon Overlord. The Achilus Crusade's forces within the Orpheus Salient were already stretched far too thinly to be effective defenders. As the Crusade scrambled to try to find reinforcements, the Tyranid Swarm moved ever deeper into the Reach. This left the Deathwatch as the only force capable of assuming responsibility for defending against the xenos incursion.

By observing different star systems and selectively choosing their targets to maximise their small but potent forces available in the Reach, the Deathwatch valiantly attempted to blunt or even halt the Tyranid attack. Whether this strategy will prove successful or not remains to be seen.


The First Encounter with Hive Fleet Dagon

The earliest encounters with what would eventually be designated Hive Fleet Dagon went almost entirely unnoticed by the Achilus Crusade High Command. The first Tyranid bioforms encountered were Genestealer Hybrids, and the members of the planet's Enforcers that destroyed them thought them to be merely hideously deformed mutants. It was not until an encounter with a full-scale infestation on the Death World of Herisor that word of a new xenos threat reached the ears of the leadership of the Crusade.

Slightly over a standard year later, Battlegroup Argo returned to Herisor to find the landscape completely changed, and no sign of the pioneers or the members of the Adeptus Mechanicus. Once again, the Iaxian Tithe Guard were sent down to the surface to investigate what happened. Once they had made planetfall, the troops who had been there previously were stunned to find that in place of a barren wasteland was now a mighty tundra that stretched as far as the eye could see. The commander of the Tithe Guard sent out scout patrols in all directions to attempt to find some trace of the missing group.

For the first solar hour or so, all was normal. No sign of the previous landing group, but nothing to indicate what happened to them. That's when all communication was lost, except for one broken transmission. The commander of the Iaxians had his communication officer relay a message to the fleet in orbit, along with his plans for dealing with this new menace on the planet's surface. Receiving an acknowledgment from command, he proceeded to carry out his mission. The Iaxians were never heard from again.

The Deathwatch Arrive

After receiving the foreboding message from the Iaxian 7th, General Curas deployed Battlegroup Cerberus, under the command of Lord Admiral Arkelius back through the Warp shadow. Her task was to send a message directly to Lord Militant Tetrarchus and any officer of the Adeptus Astartes regarding this new and terrible threat. Cerberus immediately departed back towards the Iron Collar at all possible speed. The ship stopped once, for their Navigator to realign himself with the Astronomican, and during this brief stopover they encountered the Strike Cruiser Bellaron.

Seeing it was a Space Marine voidship, Admiral Arkelius transmitted the message to them, then proceeded on towards her original goal. What she did not realise was that the Strike Cruiser Bellaron was currently under extended secondment to the Ordo Xenos to transport the Deathwatch to new locations within the Acheros Salient. Hearing the message, Inquisitor Ghent had the captain of the vessel come to a new heading. The Deathwatch headed directly to Herisor. This new information had to be confirmed with all possible speed. If the Tyranids had indeed come to the Jericho Reach, then there were now more pressing matters to deal with than the recent surges in T'au activity around the Black Reef.

Before there was any Deathwatch intervention, fifty Astartes of the Storm Wardens Chapter fought to stop the Tyranids or at least slow their advance on Herisor. Eventually the Deathwatch was sent to aid the Storm Wardens' operations on the planet. When the Deathwatch arrived at Herisor, they deployed in numbers more akin to a typical Codex Astartes planetary siege than the usual small Kill-team deployment. More than fifty Deathwatch Space Marines deployed to the surface that day. They fought a campaign that lasted nearly six solar months, until they were convinced that the menace was ended.

The Deathwatch aided the Storm Wardens with surgical strikes on Tyranid spore chimneys and synapse creatures with the support of the Strike Cruiser Bellaron in orbit. From status reports, Inquisitor Ghent became increasingly concerned when he noted that the Tyranids were holding the Chapel of Saint Aret and the city surrounding it hostage. He assumed they were attracted to a relic or something else present in the area radiating a psychic signature.

The campaign ground on for solar months and every opportunity was taken to prevent the Tyranid swarm from reaching critical mass. Ghent decided to send a Deathwatch Kill-team along with one of his trusted Acolytes to survey the chapel and recover whatever relics resided within. The Kill-team, designated Lux Veritatis, reached the chapel and reported the discovery of a relic of great power. Soon after, they were overrun by the Tyranids and called for an orbital bombardment of the area. All contact with the Deathwatch team was subsequently lost. The Lux Veritatis was later presumed dead after flyby reconnaissance reports noted the remains of armour similar to theirs and that of the Inquisitor's Acolyte strewn about the battle site.

After the end of the campaign, when the Tyranid menace had been defeated, Inquisitor Ghent had the planet declared a Death World to ward off any who would be greedy enough to attempt harvesting its natural resources. Of the original fifty Deathwatch Astartes deployed to Herisor, only twenty made it back alive.

At the same time that the Deathwatch were attacking the Tyranid force on Herisor, word of this new threat had reached Lord Militant Tetrarchus. He quickly requested the Battle-Barge Blood Sword to investigate where these creatures had come from. By tracing a line amongst the stable Warp routes, the Navigators aboard the Blood Sword came upon what may have been the first planet infected by the Tyranid swarm within the Jericho Reach. It took three long solar months of Warp travel before the Astartes of the Blood Sword were able to set foot on the planet that was once known as Zanatov's Harbour.

Zanatov's Harbour

Zanatov's Harbour was named for the legendary Rogue Trader Corsair-Captain Zanatov. This planet was one he frequented on his trade runs coming in from the Eastern Fringe of the galaxy. At one point it boasted excellent voidship repair facilities, and the lack of contact with the Imperium made an excellent place for smugglers and other members of the so-called "Cold Trade" to meet up and swap goods.

This all changed at the end of 812.M41. Early reports recovered after the fact state that many people saw what they believed to be a meteor shower in the night sky. No one thought much of it, as a meteor shower is often a good omen for voidship captains. Slowly the reports began to filter in. These were no mere meteorites that had hit the ground, but instead housed a more sinister cargo of Tyranid bio-organisms. The merchants and crew on the surface put up a decent fight, but were utterly outmatched by the lethal organic killing machines. Some managed to make their way to their voidships, but found that larger organisms were floating through the void, firing caustic projectiles of a biological nature.

None survived the onslaught of the ravenous beasts. All that were on-planet were devoured, their genetic patterns added to the primordial soup that comprises Hive Fleet Dagon's gene-pool. Ships in orbit were left abandoned. Most had had their hulls ruptured in hundreds of places by Tyranid bio-spores attaching to the hull that ate their way inside. Any ships not completely wrecked were now floating abattoirs, a sickening testament to the utter brutality of a Tyranid swarm on the warpath.

So it was that Brother-Captain Kristoff and his company of Templars of Blood Astartes made their way to this graveyard of a planet. They expected to have to use the Battle-Barge's bombardment cannons to clear the way of Tyranid vessels, and then deploy Thunderhawk gunships, as they would not be able to get close enough to use Drop Pods. What they actually encountered was something far worse.

When the Blood Sword translated back into realspace, it found nothing but a dead planet. Every bit of biological material had been stripped bare from the planet's surface. Setting down in their Thunderhawks, the Templars began a thorough search of the planet for any clue as to how the massive Hive Fleet had arrived in the Jericho Reach.

Realising that he could not take a full Battle Company off of the front lines, Brother-Captain Kristoff left behind a small contingent of his available Space Marines to continue the investigation. Currently, there has been no communication from the Space Marines left behind that day, but the commanders of the Orpheus Salient still hold out hope that some day there will be news that can help them turn the tide of this war.

The Tide Begins to Turn

Backed into a corner by the ever encroaching swarm of Tyranids, the Astra Militarum forces in the region began to retreat towards the Iron Collar. Lord Commissar Theren and General Arkelius pulled almost all of the Imperial Guardsmen who were not already engaged with the Tyranids back to the Feral World of Treyen. Here, they determined, was their line in the proverbial sand. They would fall back no further and they would either die to the man, or push the foul xenos back into the Warp from whence they came.


A largely temperate world, Treyen's population is centred primarily in its western hemisphere. The last Imperial Census had the population at roughly 250,000 with an average technology level equivalent to that of the Bronze Age. The primary star within the system is entering into its last stages of life, and as such solar flares are beginning to spread a blanket of radiation around the planet. This has a nasty habit of causing long-range Vox transmissions to be unreliable at best, but it also seems to have an equal effect upon the psychic communications of the Tyranids on-planet. Treyen was chosen as a suitable battleground by the leaders of the Orpheus Salient for these specific peculiarities.

When the Achilus Crusade first encountered the planet Treyen, it was found that the natives there worshipped their sun as a god. While this deity provided them with warmth, he could also bring terrible vengeance upon them when he was angered. The Ecclesiarchy had little trouble in slightly altering the perceptions of the natives so that the God-Emperor of Mankind was seen in the same light as their false sun god. He would provide them with warmth, shelter, food, and protection, but if they ever angered Him or His chosen representative, He would strike down upon them with a furious anger the likes of which they had never seen before.

While the Departmento Munitorum was attempting to calculate what the planet's tithe grading would be, it was discovered by an adventurous group of Imperial Guardsmen that the large native beasts had a unique pelt that, when skinned, had the ability to change colouration with the lighting. With this discovery, the planet's primary export was quickly changed from baseline foodstuffs to luxury goods. Rumour has it that General Derian Arkelius himself has his Crusade dress uniform made from the hide. No one has seen this uniform, but it would fit his public persona.

After classifying and settling the planet, a small defence force was left behind, mainly to hold off any Orks tempted to raid this deep into the Crusade's line. Much of their time on planet was spent with very little to do, as the native population was fairly tame and had nothing but love for the God-Emperor. Occasionally there would be a small uprising by one of the tribes that had been displaced when the Imperial Guard claimed certain land as their headquarters, but savages with swords and axes do very little against trained men with Lasguns. At the beginning of 815.M41, the small garrison received a rather abrupt wake-up call. Lord Commissar Theren and Battlegroup Cerberus arrived in force to stand in the way of a new xenos threat that was approaching.

When Theren landed, he exited his lander quickly and set up a command post inside the Astra Militarum headquarters for himself and the rest of the Triumvirate. Immediate orders were given to begin erecting defensible positions. Swarms of Adeptus Mechanicus Servitors skittered off of the lander in his wake and began stripping the compound of all materials needed to enhance the base's defence. Over the next two solar weeks thirty-three full regiments of the Astra Militarum, almost the entirety of the Orpheus Salient complement, landed with the Scintillan 84th and General Derian Arkelius at their head.

Artillery pieces were quickly placed in defensible positions. Sentinels and snipers were sent to reconnoitre the surrounding terrain. Lord Commissar Theren barricaded himself in his command post with General Arkelius in an attempt to find a way to effectively hold the line at Treyen. It wasn't until the fifteenth day that Theren received three communications. The first was from the Lord Admiral Arkelius, saying that if the shadow being cast in the Warp was any indication, the Tyranid fleet was massive. The second came from the Dark Sons Chapter of Space Marines. The 1st Company with its squads of Terminators would be arriving in three solar days. The third was from his fleet Astropath. The Tyranids would arrive in two solar days.

When the Tyranid fleet arrived, Lord Admiral Arkelius proved to any doubters exactly how she had achieved her position. Fully one-third of all Tyranid vessels were destroyed in the naval engagement above Treyen. Her fleet was badly damaged, but she was still able to order her picket ships in to provide close fire support for the upcoming battle. On the ground, despite the situation in orbit, the task ahead of the sixteen million Guardsmen seemed hopeless. What appeared to be a monsoon of living monstrosities began pouring out of the sky and wave upon wave of hungry xenos beasts rushed towards the Imperial battle lines. For twenty-four solar hours the entire planet of Treyen was a battlefield. Millions of Imperial Guard were killed, and even more were wounded.

Eighteen solar hours into the engagement, streaks of light came hurtling towards the planet's surface. Over the communication system came a message telling Lord Commissar Theren to order a full counter-assault in exactly one solar hour. Attached to the message were the authorisation codes of the Deathwatch. Precisely one hour later, the Tyranid horde fell into absolute disarray, and Lord Commissar Theren sent planetwide orders to begin the counterassault. Five solar hours later, Lord Commissar Theren met up with the Deathwatch Kill-teams that had been inserted on the planet via Drop Pod. These Kill-teams had destroyed the largest Tyranid bioforms, thus disrupting the creatures' ability to psychically communicate with one another. With no enemy leadership in place, the Imperial Guard were able to take advantage of the Tyranids' confusion and drive them back into an open area where the fleet in orbit could bombard the xenos.

When compiling his after-action report, General Arkelius noted that if the Tyranids had continued engaging the fleet in orbit, it would have been impossible for the Deathwatch to get close enough to be successful. By committing to the all-out attack too early, the Tyranids had cost themselves the battle. When the Dark Sons arrived the next day, they were quickly able to hunt down and remove all obvious signs of Tyranid infestation. All three Imperial Guard commanders were acknowledged for their bravery and skill in handling what would normally have been an impossible situation. The one drawback was that the attacking Tyranid force had now splintered apart. One splinter moved towards Hethgard, and the other appeared to be heading for Tryphon. The Deathwatch are currently keeping a very close eye on Treyen, as they need to make sure that the planet is thoroughly cleansed.

The Bold Decision

Fresh from their successful defence of Treyen, the Triumvirate decided that they would now have to make a gamble on their next move. The Tyranid infestations must be wiped clean from the Jericho Reach, so as not to risk another splinter fleet moving somewhere else and continuing the destruction. Lord Admiral Arkelius suggested that they concentrate their naval resources into one massive fleet and overwhelm the Tyranids at every encounter. Her brother suggested luring the xenos to either an uninhabited or sparsely-inhabited world and just bombarding them from orbit.

Lord Commissar Theren had another idea. Battlegroup Cerberus would swing coreward and skirt the edges of the Orpheus Salient until they had reached the end of the push. At this point they would turn about and begin to give chase after the trailing edges of the Hive Fleet. Battlegroup Daedalus would move rimward and skirt the other edge of the Salient. They would then hold position until they received acknowledgment that Battlegroup Cerberus were in place. At this point, the two fleets would converge on the Tyranids and make them pay for the suffering that they had caused the Imperial Crusade. Only time will tell if their plan is successful.

Current Status

"We have begun to encounter some communications difficulties within the Salient. These seem linked to activity near the Phonos System. I am personally taking Battlegroup Argo there, to identify the issue and get it quickly sorted. I am confident that it is not a matter of serious concern."
—General Mikal Curas, in his last dispatch to the Lord Militant

Imperial forces have continued to analyse Hive Fleet Dagon, but any measurement based upon Tyranid activity is confounded by the Shadow in the Warp. As the xenos presence prevents Imperial forces from effective communication, it is likely that additional worlds have fallen to the alien threat without the Achilus Crusade or even the Deathwatch becoming aware of the attacks. Consequently, any analysis that depend upon such data collection must be carefully considered in light of this imposed limitation.

Though Herisor was the first world to fall to the Tyranid threat, attacks upon Freya and Zanatov's Harbour also occurred in short order. Timing of these early attacks is difficult to gauge, as there was little contact during the attack and substantial time may have passed before investigations revealed the Tyranid activity. Best estimates suggest that all three of these worlds were under assault at the same time. Since these initial attacks, reports have begun pouring in from worlds all across the rimward edge of the Reach.

Much of this information comes from bedraggled survivors who managed to escape on Warp-capable vessels just as their worlds were being consumed, and Crusade leadership has struggled to sort through the mountains of contradictory reports. Some headway has been made in stalling the relentless advance of the Hive Fleet, but most of it has been due to the efforts of the Triumverate who are operating deep within the Shadow in the Warp.

The agents of the Deathwatch and the Ordo Xenos have had much more luck than the overwhelmed Crusade leadership. Making use of their array of rapid strike vessels, the Deathwatch has sent Kill-teams into the swarm to collect samples for analysis, scout the Hive Fleet's progress into the system, and to strike at high-value targets when the opportunity rises. However, even the elite and well-organised Deathwatch Space Marines have difficulty contending with the complete communications blackout imposed by the Shadow in the Warp. Watch Fortress Erioch will go great lengths of time hearing nothing from the rimward edge of the Reach, unsure if the Watch Stations there are even still standing.

Based upon the time stamps of various incident reports, Hive Fleet Dagon has no fewer than three sub-fleets. Reports of historical Tyranid strategies suggest that a Hive Ship rarely leaves a star system prior to completing the assimilation and destruction of all planets within that system. As there are large-scale attacks currently in progress on no fewer than nine star systems in the Reach, Crusade tacticians, including the Lord Militant, have been unable to reconcile this broad battlefront with the notion of a limited engagement by a Tyranid splinter fleet.

Each of these sub-fleets requires a separate Hive Ship to coordinate its Hive Mind. In order to ultimately defeat the Tyranid attack, each subfleet must be eliminated, so that the Hive Mind throughout the Reach may be compromised. Until that happens, surviving Hive Ships could travel to a contested system, throwing their added might into a battle. Coordinating the battle plan to simultaneously defeat all of these ships may be impossible while dealing with the limitations of astrotelepathic communication in the presence of the Shadow in the Warp.

Hive Fleet Dagon Tactics

"There is no evidence that these so-called "Tyranids" are a reasoning opponent. The xenos are surely incapable of using any sort of advanced tactics. Rather they are little more than an all-consuming organism. Overcoming them should be a simple matter of applying thought and leverage to determine their vulnerabilities."
—Bishop Josef Daven to Inquisitor Kryptman

Because of the limitations imposed by the Shadow in the Warp, Imperial analysts believe that Hive Fleet Dagon was identified only after it had completed several successful assaults within the Jericho Reach. As a consequence, it is uncertain whether the Tyranid forces are the spear tip of a much larger force, or if they simply represent the surge in growth that would occur after absorbing the bio-mass from several of the region's planets. If these xenos began their intrusion with a limited force, it may be that the earliest attacks exhibited were undertaken in a conservative manner.

Unfortunately for the Achilus Crusade forces, it is clear that the Hive Fleet has met with a great deal of success. At this time, the Hive Fleet's resources are generally well supplied with bio-mass. As a consequence, the Tyranid incursion represents a substantial threat to all other life within the Jericho Reach. These xenos are capable of exploiting the raw materials that they have captured to launch attacks that utilise near-overwhelming force against prey worlds. With each triumph, their resources are renewed and their capacity for destruction becomes further enhanced.

Achilus Crusade and Deathwatch forces have confirmed intrusions by Tyranid Drone ships within more than twenty star systems of the Orpheus Salient. Imperial forces fear, but have not confirmed, that the majority of these intrusions coincide with insertions of Genestealers or Lictors to habitable planets. Imperial analysts have thus far had no luck in tracing a pattern of how Hive Fleet Dagon's Vanguard Drone ships have been scouting the Reach. This, combined with a lack of knowledge regarding the lifespan of the Vanguard Drone ships, leaves Imperial forces helpless to defend against these forward scouts of the Hive Fleet. If each such creature is capable of identifying and infecting multiple targets, a single vessel surviving could soon draw Hive Fleet elements to dozens of planets.

Deathwatch agents are currently monitoring reports that could indicate the earliest stages of Tyranid scouting activities within more than a dozen star systems. Based upon current data, the Deathwatch believes that this substantially exceeds the number of planets that the Hive Fleet is currently capable of engaging. While Deathwatch agents have confirmed Tyranid activity in all systems that have been attacked by the full might of the Hive Fleet, not all systems that exhibited a scouting presence have been attacked. This suggests that the Hive Fleet may be plotting out its travel through the Jericho Reach. The Hive Mind may be preparing for an extended incursion, carefully selecting which planets might offer the most biomass return, so that environments of less strategic value could be targetted after its resources are better established.

When the Tyranid Hive Ships enter a star system, they have consistently demonstrated a specific focus upon immediately assaulting any habitable planets. While this may seem an obvious strategy, it is important to note that Hive Fleet Dagon has largely ignored Imperial void stations and outposts on otherwise barren planets and moons. Imperial vessels have generally only been attacked after they directly engaged the Tyranid void travellers. It might offer further evidence that the Hive Mind is operating in a conservative fashion, or might simply be that for some reason the Hive Fleet is unable to accurately identify these elements as worthwhile targets.

Once Hive Ships enter the orbit of a prey planet, they have consistently begun their attacks by launching vast numbers of Mycetic Spores towards the world's surface. In the earliest reported instances, this initial attack wave was so numerous that defenders were overwhelmed within solar days. More recently, Crusade forces have successfully survived this initial attack. On the worlds of Castobel, Atonement, and Hethgard, Imperial defenders managed to repel enough of the spores that the battles for control of these planets have become protracted engagements. On Avalos and Treyen, Imperial defenders even managed to repulse the initial Tyranid attack, causing the void-faring Tyranid creatures to leave those systems. There are many speculations as to why the Tyranids fled; some Imperial analysts believe they moved on to easier prey, while more military minds speculate the creatures are attempting deliberate feints to draw Imperial defenders away from other worlds.

If this is the case, it may be that planets further from currently engaged systems could be attacked unexpectedly. The Orpheus Salient at present has a very limited number of defenders held in reserve. The vast majority of these are currently deployed upon those planets closest to the Tyranid incursion. In the event the Hive Mind chooses to bypass those planets, and instead targets worlds deeper behind enemy lines, the consequences could be catastrophic. Such a tactic might also explain the extensive number of systems where scouting activity has been confirmed.

The potential for this strategy is increased due to the absence of a Tyranid supply line. Once a Hive Ship leaves a system after devouring its habitable planets, nothing is left behind. A Hive Ship and its support vessels effectively carry all of its swarm into each new warzone. Once a system is engaged, it must triumph quickly or the vessels possess ever-fewer creatures to commit to an attempt to consume an alternative target. While these failed and extended engagements could increase the chance of an ultimate Imperial victory, they might also provide evidence that Hive Fleet Dagon is actually carefully preparing to expend all of its resources upon an unsuspecting target.


"Before we can come to understand the threat presented by Hive Fleet Dagon, we first must come to grips with the organisms that comprise it. Only by studying their ontogeny can we begin to understand their capacity."
—Brother Codicier Taelon
Dagon's Warriors

Tyranid Warriors of Hive Fleet Dagon, raging on the battlefield

The Tyranids of Hive Fleet Dagon are similar to those which were encountered during Hive Fleet Behemoth's assault. However, additional Tyranid creatures have been observed among the forces of Hive Fleet Dagon. There have also been subtle changes within the appearance, but not the tactical role, of some of the previously identified Tyranid strains. These variations have included exoskeletal structures, colourations, and the most commonly observed weapon biomorph symbiotes used by the different Tyranid strains.

The most distinctive change shown by Hive Fleet Dagon is a variation in the hues of the different Tyranid creatures. The carapace on specimens from Hive Fleet Behemoth typically ranged from jet black to a deep blue. The unprotected skin of those bioforms was typically a bright red. In contrast, the exoskeletons of Hive Fleet Dagon's bioforms are generally dark grey or a blue close to that used by the Ultramarines Chapter. Where the xenos' flesh is unprotected, it is a burgundy colour.

Weapon symbiotes employed by the various Tyranids also show a substantial change in frequency from those observed during Hive Fleet Behemoth's forays into Ultima Segmentum. Specific instances within commonly encountered creatures are addressed below. Nonetheless, the consensus variants have been shown to be statistically different among parts of Hive Fleet Dagon. As this incursion has been in progress for less than five standard years at the time of this report, this may be an anomaly due to the environmental conditions and the defenders present on the worlds that have been invaded to date. This evidence suggests that Hive Fleet Dagon is a distinct entity from Hive Fleet Behemoth, but does not definitively confirm a separation between the two incursions.

In addition to symbiote modifications, the Tyranids found within Hive Fleet Dagon have shown an increased propensity for toxicity. A substantial number of otherwise characteristic Tyranid bioforms have presented with venomous sacks near their claws and fangs. These toxins substantially increased the mortality rate among Imperial casualties within the Orpheus Salient. Further, these toxins have shown a substantial range of variation even within planetary environs. Imperial medicae personnel have been unable to identify an antiserum that works consistently against the toxins.

Distinctive Specimens

Several Tyranid variant strains have been observed within Hive Fleet Dagon that are believed to be completely novel. Of these, a few have generated legends and lore among the Imperial forces that oppose them. Tech-priests seem unable to discern whether these specimens are specific individuals of their species or variant strains. It is, however, clear that these examples are consistent in their tactical approaches and seem capable of learning from past encounters. Some reports indicate that members of these strain variants have returned to the battlefront after being slain in battle. It is unclear if this indicates that the Tyranids have a mechanism for resurrecting these bioforms, or if the later encounters are evidence of additional specimens:

  • Dagon Overlord - First encountered during the brutal warfare on the world of Castobel, this specimen is believed to be a variant of the Hive Tyrant strain. The Dagon Overlord has been identified as active within many of the systems under assault within the Orpheus Salient. This monster is known for its malicious streak and its ability to drive lesser Tyranid strains into an even more hideous fervour than is typically observed. As is often seen amongst Hive Fleet Dagon bioforms, this specimen is exceptionally toxic, constantly dripping with venom.
  • Mist Reaper - First observed on Xyan, this variant of the Lictor strain has been recently observed on other worlds of the Orpheus Salient. The Mist Reaper invariably works alone, generally long before Tyranid forces assault a prey world. This monster is responsible for the deaths of hundreds of Imperial citizens who believed that they were safe, far from any conflict lines. Members of the Ordo Xenos' Divisionis Biologis postulate that the creature has a specific knack for overcoming Imperial security measures, though this has not yet been confirmed.
  • What Lies Beneath - First identified during a hive city assault on Castobel, this horror is believed to be a variant of the Trygon bio-construct. Always accompanied by swarms of Hormagaunts, What Lies Beneath is characterised by attacks upon Imperial structures far from any battle lines. Reports indicate that this nightmare is capable of burrowing through even the thick fortifications of plasteel and ferrocrete required by the foundation of an Imperial hive city. Imperial analysts are currently attempting to identify what draws the creature to its targets, so that they might find a means to isolate and eliminate the threat it represents.


  • Deathwatch: The Achilus Assault (RPG), pp. 45-46, 51-55
  • Deathwatch: The Jericho Reach (RPG), pp. 170-173
  • Deathwatch: Know No Fear: History of the Jericho Reach (RPG), pg. 11
  • Deathwatch: Mark of the Xenos (RPG), pp. 33-34
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