- "There is a cancer eating at the Imperium. With each decade it advances deeper, leaving drained, dead worlds in its wake. This horror, this abomination, has thought and purpose which functions on an unimaginable, galactic scale and all we can do is try to stop the swarms of bio-engineered monsters it unleashes upon us by instinct. We have given the horror a name to salve our fears; we call it the Tyranid race, but if it is aware of us at all it must know us only as Prey."
The Tyranids are an extragalactic composite species of hideous xenos that is actually a space-faring ecosystem comprised of innumerable different bioforms which are all variations on the same genetic theme. The Tyranid race is ultimately dedicated solely to its own survival, propagation and evolutionary advancement. The Tyranids collectively form a monstrous superorganism that travels across the universe in their great Hive Fleets of biomechanical Hive Ships, systematically consuming all other biomatter to enable its own rapid evolution and reproduction. All Tyranid organisms are synaptic (psychically-reactive), and each Tyranid creature within a Hive Fleet shares and contributes to a communal Hive Mind, which allows the trillions of beings comprising the Tyranid Hive Fleets to communicate and organise instantaneously on a staggering scale.
The mentality of the Tyranid approach to warfare can be described with the phrase "quantity has a quality all its own". From the "lowly" Ripper, to the deadly Hive Tyrant and beyond, the signature of the Tyranid species is that they overwhelm their foes with sheer numbers, reproducing massive numbers of highly virulent organisms in record time from the biochemical soup that they derive from the biospheres of the worlds that they consume. The components of a Tyranid Hive Fleet travel almost exclusively in large groups known as swarms that possess specialized biomechanical creatures for destroying and consuming a wide variety of prey life forms. Tyranids have evolved sophisticated methods for facilitating genetic transfer across species boundaries. As a result, a significant goal of any Tyranid invasion is acquisition of useful new biological traits from other lifeforms. These are used by the Hive Mind to enhance the Tyranids' effectiveness in consuming new worlds to gain more of the necessary organic raw materials for further reproduction. All Tyranids are reproduced by a single, highly intelligent female bioform known as a Norn-Queen. A Hive Fleet's Norn-Queens are the most important Tyranids within the fleet, for if they are injured or killed the Tyranids cannot reproduce their numbers from the captured bio-mass. As a result, Norn-Queens can be found only at the heart of the largest and most-well defended Tyranid Hive Ships.
The Tyranids were initially described in the 1st Edition of Warhammer 40,000 (Rogue Trader), with their basic form not too different from that used today. Their only additional troop type was an enslaved alien race, the Zoat. At that time they were not an important race in the Warhammer 40,000 universe. In later editions they became a playable faction in their own right, and it was revealed that the Genestealers (first popularized in Space Hulk) were in fact part of the advance reconnaissance element of the main Tyranid Hive Fleets.
The first recorded contact between the Imperium and the Tyranids places their appearance in the Eastern Fringes of the galaxy in 745.M41. However, it is rumoured that the Ordo Xenos of the Inquisition had identified possible appearances of this xenos species as far back as the 35th Millennium.
The xenos emerged from the intergalactic space of the Local Group of galaxies, their Hive Mind drawn to the Milky Way by the psychic beacon of the Astronomican transmitted by the Emperor's presence in the Warp from Terra. The first officially recorded contact with the Tyranids for the Imperium of Man came during a Tyranid attack on an Ocean World called Tyran, and from there Hive Fleet Behemoth continued directly towards the center of the galaxy, consuming all the worlds in its path. The Tyranids were defeated, barely, by the efforts of the Ultramarines Chapter of the Space Marines during the Battle of Macragge, although the Ultramarines suffered devastating losses that would take centuries to replace.
In 942.M41, Commissar Ciaphas Cain, while on a mission in the Ice World Nusquam Fundumentibus, discovered hibernating Tyranids buried deep in the permafrost; the swarm was apparently carried to the planet by a Hive Ship that had crashed on the planet many millennia before, prior to any human colonisation. Members of the swarm and subsequently, the Hive Mind, was awakened, but this swarm was eventually defeated. However, the Inquisition was unsettled by the fact that the Tyranids had developed a presence in the galaxy possibly before even the start of the Age of the Imperium; it is not known whether the crashed bio-ship was on a scouting mission when it was lost, was a casualty in a pre-Imperium Tyranid invasion force that was defeated by unknown adversaries, or part of a plan by a Tyranid super-intelligence that may have "seeded" the galaxy with many such slumbering broods.
In 993.M41 the Tyranids returned to the galaxy with Hive Fleet Kraken which, instead of assaulting its targets as a single massed Hive Fleet, split into countless smaller fleets, each enveloping whole star systems before reinforcements could arrive. The brunt of this new attack was borne by the Space Marine Chapters known as the Scythes of the Emperor and the Lamenters; the former Chapter was almost completely destroyed. Though the backbone of the Hive Fleet was broken by its defeats at the Battle of Ichar IV and at the Eldar Craftworld Iyanden, the cost to the Imperium was still great and many splinter fleets broke off from the Kraken to later wreak havoc deep within Imperial space.
Only a few years later, in 997.M41 Hive Fleet Leviathan unexpectedly appeared from "below" the plane of the galaxy (on the Z axis) and attacked from two points, cutting off large portions of the galaxy from reinforcements. Just as it seemed the defenses of the Segmentum Solar and perhaps Terra itself would be tested, the Tyranids were distracted by being deflected into the star system of a powerful Ork empire. While the Orks are managing to stall the main Tyranid Hive Fleet's advance, they are likely to reemerge from these battles, victorious and stronger than ever after having absorbed potent Orkoid genetic material into their own genome pool.
The Tyranids are actually an extragalactic species, born somewhere beyond the void that separates the galaxies of the Local Group. Tyranid Hive Fleets travel through space by using gigantic, organisms genetically engineered to travel through a vacuum known as Hive Ships, which move in groups which can be likened to very large locust swarms. Typically, Tyranid Hive Fleets move in ad hoc formations known as Tendrils, migrating to nearby inhabited planets after consuming all the biological and organic material on a recently invaded planet and breeding, often reproducing many times their original number. Hive Fleets travel with superluminal speed, though they never enter the Warp. Instead, by using the specialized psychic power of a selectively evolved Hive Ship, they manipulate the gravity fields of star system to achieve faster-than-light travel. The massive Warp presence of the Tyranid Hive Mind, however, manifests itself in that realm through the Shadow in the Warp phenomenon. The current collection of Tyranid Hive Fleets have migrated to the Milky Way Galaxy, presumably after overpopulating or overfeeding in other nearby galaxies of the Local Group. Given that each Tyranid Hive Fleet has approached the Milky Way from a different direction, this may imply that the Tyranids have consumed a disturbingly large number of nearby galaxies.
Tyranid Hive Fleets consist of millions of biomechanical craft, each serving as host to an untold number of symbiotic organisms. These creatures evolve and spawn from a variety of geno-organisms in the ships' reproductive chambers. All these creatures are born to service the ship, and the ship in turn exists only to service the needs of the Hive Fleet. Whereas other armies like those of the Imperium and the Tau fight for conquest or self-defence, and the Forces of Chaos and the Ork clans battle merely for the chance to wreak violence and havoc, the Tyranid Hive Fleets are driven by the will of the Hive Mind, which itself is motivated by the most ineradicable instinct inherent to all lifeforms - reproduction, and through reproduction and the acquisition of new genetic traits, evolution to a better adapted form.
A fully mobilized Tyranid Hive Fleet strikes shock, awe, and terror into even the most stalwart of humanity's defenders. Even when the xenos threat is eliminated (at great cost), it will not be long before another Tyranid migration emerges to take advantage of the situation. This is what makes the Tyranid species such a threat: it is an evolved meta-predator capable of out-producing, out-consuming, and out-lasting all other species it encounters, having done so on a disquietingly unknowable number of prior occasions across a vast swathe of intergalactic space.
All Tyranids possess a common psychic bond, known as the Synapse. This bond enables the Tyranid swarms to think, perceive, and act as a single great super-organism, providing nearly seamless co-ordination and control within a Tyranid invasion force so numerous and extensive as to be completely uncontrollable otherwise.
From the smallest feeder organisms, to the microbes that decompose new biomass; from the sessile and rooted flora-like forms, to the huge tendril-like shoals of the Hive Fleets, every Tyranid organism has a place within the will of the Hive Mind. The lesser and smaller creatures are mindless and instinctive animals, plants and bacteria, performing functions with no conscious oversight or commitment, while larger and more complex creatures can make decisions appropriate to the situation and form an integral if minuscule part of the Hive Mind's distributed sentient awareness.
Functioning in perfect unison, coordinated by powerful psychic imperatives transmitted through the Tyranid communal sentience that is the Hive Mind, Tyranid fleets, swarms, and broods do not have a singular command structure, but rather form a synaptic web of psychic influence and feedback. Situated within this tangled web are specialised Synapse Creatures whose slightly more advanced brains function as psychic routers, buses, and hubs, co-ordinating and policing the riotous cacophony of the collective brain power of a mass organism that is sometimes larger than most planets. Without the localised control provided by these organisms, the swarm can quickly falter, and some Tyranid creatures may revert to animalistic behaviors, when individual will and situational instincts come into conflict. Often swarms will subdivide into smaller packs of creatures still capable of consensual behavior among themselves. The Synapse Creatures that channel the commands of the Hive Mind are mostly, if not all, potent individual psykers. How any of this is done without drawing the attention of countless daemons of Chaos or the other psychic predatory entities of the Warp into the midst of the Tyranid swarm is unknown and possibly unknowable to the humans of the Imperium.
Tyranid Hive Fleets do not travel through the Warp like Imperial starships. Yet, the Hive Fleets' incredibly fast rate of advance into the galaxy belies the argument made by some that they do not possess a mode of faster-than-light travel. Whilst it is true that the Tyranids are forced to remain at sublight speeds while within the gravitic boundaries of a planetary system, they are capable of superluminal velocities when travelling through interstellar space. This capability is the result of a small Tyranid bio-ship classified by the savants of the Imperium of Man as a Narvhal. Unlike most Tyranid bio-ships, the Narvhal is almost completely defenceless, and possesses almost no bio-weaponry and only a very thin protective carapace. A cluster of monofilament spines on the Narvhal's bow allow it to take in a wide variety of sensory input, including a broad spectrum of gravimetric and electromagnetic signals. Using these sensors, the Narvhal can detect new planetary systems at extreme interstellar distances. In some unknown manner it then makes use of the origin star system's own gravity and creates a compressed space-time transit corridor through which the Narvhal and other Tyranid bio-ships can traverse interstellar distances. This form of space-warping travel cannot be used near strong gravitational sources as they overwhelm the Narvhal's hypersensitive navigational sensors. As a result, a Tyranid Hive Fleet must use more conventional forms of biologically-induced reaction-based propulsion during the final approach to a new star system, which can slow their arrival by years or even entire decades. Whilst this form of propulsion is ultimately slower than a reliance upon the Warp-Drive, it is a great deal more reliable and allows the Tyranids to move slowly, if implacably, across the galaxy. However, the Narvhal's manipulation of a star system's gravity does sometimes produce unintended side effects. A destination world can suffer from earthquakes, solar flares, tidal waves and other natural disasters produced during the interval during which the Hive Fleet is in transition through the space-time transit corridor. This chaos only further benefits the Tyranids' invasion, however, as the defenders of the target world will have their resources bound up in dealing with these problems when the swarm finally arrives in orbit and the first Mycetic Spores begin to fall.
Tyranid Combat Doctrine
Tyranids often attempt to first conquer a planet through subterfuge and infiltration. Space Hulks and other derelict spacecraft are infested with Genestealers, which quickly familiarise themselves with the layout of their new home, then enter hibernation.
When the Hulk is eventually discovered by Imperial authorities, the Genestealers attack the exploration crew, sometimes killing some crew members, but always leaving at least one survivor who is implanted with a seed, a form of Genestealer reproductive virus that contains specially-engineered Tyranid DNA. This infestation is never fatal, but instead the virus' genetic material subtly alters the victim's DNA, producing in them a strong urge to mate created by the stimulation of the individual's sex hormones. The Genestealer DNA will be incorporated into the host's germ cells and so any child that results from this union will be a Genestealer Hybrid, which now has the complete loyalty of its parents through a psychic bond. The Hybrids continue to breed and multiply among the population of the host species, eventually forming a Genestealer Cult. As the Cult grows in numbers, it begins to spread its influence throughout the planet's political and social structure, placing its members in positions of power within the government and the military. At the same time, the Cult's Hybrid members begins to emit a collective psychic signal through the Warp that acts as a beacon for the approaching Tyranid Hive Fleet.
As the Tyranid Hive Fleet nears the doomed world, the Genestealer Cult, potentially numbering in the millions by this point, goes into action, instigating a worldwide rebellion with the goal of weakening the planet's defenses against the approaching Hive Fleet. The Hive Fleet will also seed the planet with Tyranid organisms, which will begin to biologically alter the planet's climate, surface and ecosystems to make it easier to consume. If the Hive Fleet is victorious, the fleet will descend to the planet, inhaling the atmosphere, drinking the seas, and basically consuming all organic biomass until nothing more than a lifeless ball of rock remains.
On the battlefield, Tyranid tactics are based around the notion of superior numbers, as they generally try to outnumber the enemy fifty to one. Tyranids overrun opposition in close combat, closing faster than most armies. They possess few ranged weapons, but their sheer numbers and close combat specialisation makes up for the slaughter if they are led by a capable commander.
Forces of the Tyranids
- Hive Tyrant
- Old One Eye
- Tyranid Warrior Prime
- Tyrant Guard
- The Parasite of Mortrex
- Doom of Malan'Tai
- Hive Guard Brood
- Lictor Brood
- Pyrovore Brood
- Venomthrope Brood
- Ymgarl Genestealer Brood
- Zoanthrope Brood
- Tyranid Warrior Brood
- Genestealer Brood
- Termagant Brood
- Hormagaunt Brood
- Ripper Swarm Brood
- Gargoyle Brood
- Hive Crone
- Mycetic Spore
- Ravener Brood
- Red Terror
- Sky-slasher Swarm Brood
- Spore Mine Cluster
- Tyranid Shrike
- Biovore Brood
- Carnifex Brood
- Trygon Prime
- other Bio-Titans
Biomechancial War Machines
The Tyranids do not build their starships and weapons from metal and plastic like the other intelligent races of the Milky Way Galaxy; instead, they use gene-splicing and bioengineering to grow them from the organic biomatter harvested from the planets they consume. Every weapon, gland and projectile used in their armies is a bioengineered Tyranid organism in its own right, from the spores polluting the atmosphere, to the grotesque spires that burst from the tortured ground during an invasion.
- " Though never a verdant world, the lifeless ball of rock that we discovered was unrecognizable as Tyran Primus. The creatures that did this are a threat to the galaxy and must be exterminated by the light of the God-Emperor."
- —Inquisitor Kryptman, concluding his report on the ruins of Tyran Primus
- Reconnaissance - The earliest stages of a Tyranid infection are best characterised by their subtlety. At this stage, the xenos evaluate the planet’s viability for attack and begin to infect the native life forms. The three species most active during this stage are Vanguard droneships, Lictors, and Genestealers. These biomorphs share two critical characteristics for identifying new target planets and performing infi ltrations: stealth and independence. All of the organisms involved have physiological abilities that are focused upon concealment. These talents are exploited to the utmost, so that they can initially observe the native environment safely. As there are often a very limited number of Tyranids involved at this stage, these specimens exhibit an uncharacteristic degree of self-preservation. The creatures are clearly aware that they must survive and propagate before the invasion may proceed. These specimens are distinctive from most of the Tyranid horrors in that they are also capable of stable independent action. The vast majority of known Tyranid organisms are incapable of coordinated activity when separated from the psychic emanations of the Hive Mind. As these creatures must be capable of acting when light-years distant from the swarm, they manifest a greater degree of intelligence and animal cunning than would otherwise be expected. This becomes most evident in the often unexpected subtlety of their plans. Vanguard droneships depend upon speed, their relatively small size, and their reduced psychic and propulsion signatures to enable them to quietly scout out new systems. In many cases, a Vanguard droneship will deposit a portion of its cargo onto the surface of a likely planet, and then quickly leave the system to scout out targets in other systems. As their time in the system is both brief and stealthy, Imperial agencies may remain completely unaware of the foreboding intrusion. In those cases when a droneship is identified, it must immediately be considered the highest priority target in the system, as destroying it before it can deploy its cargo may significantly delay any Tyranid intrusion. Lictors are masters of unseen reconnaissance. After insertion from a droneship, these xenos immediately begin scouting the wilds of the newly identifi ed planet. Using their feeder tendrils, they analyse the atmosphere, mineral availability, and the characteristics of all life forms. In addition, these fierce predators also target isolated animals and even sapiens to absorb their memories as they devour them. This information is compiled and sent back to the Hive Mind as soon as a node within range is available. Any Lictor that can be eliminated prior to the start of a full Tyranid invasion can substantially slow the attack, as the invading xenos are less optimised for the planet’s ecosystem. Genestealers are the most insidious of these early invaders. As they scout out the planet, they also infect the planet’s fauna with Tyranid genetic material. The corruption of the planet’s native gene-code eventually results in hybrid creatures that are subject to the will of a Broodlord or other representative of the Tyranid Hive Mind. It is also believed that Genestealers may use their cunning and stealth to infiltrate planets without the aid of a droneship. Specimens have been found on abandoned space hulks and hidden among the cargo holds of Warp-capable vessels. These creatures must be eliminated with extreme prejudice, before they establish a breeding nest and a community of dedicated hybrid organisms. Once Tyranid species have established a toehold on a planet, their strategy soon changes. Successful integration of the planet’s wildlife triggers these infi ltrators to emit a psychic call to the swarm. This call draws a fleet of vessels, including a hive ship to the system. The arrival of the hive ship and its escorts heralds the next phase of the invasion.
- Infestation - The arrival of the hive ship and its escort vessels heralds the next stage of a Tyranid system invasion. As a powerful node of the Hive Mind, the hive ship disrupts the Warp in a radius of several light years. By the time one of these massive voidfaring creatures has arrived, it is often too late for a planet to send out an astropathic cry for help. Even vessels sent to defend a system under threat of Tyranid attack may be unable to exit the Immaterium in a system that has come under the influence of the Shadow in the Warp. Once the hive ship has come into range of a target planet, it immediately begins to launch a rain of mycetic spores into the atmosphere and towards the planet’s surface. Some of these pods are filled with microbial life. These hostile micro-organisms immediately begin to change the planet’s atmosphere, oceans, soil, fl ora, and fauna. Complex organic molecules are broken down and recreated in formats that are best suited for absorption by the swarm. Other spores bear more complex Tyranid creatures. Some of these, including the various strains of Gaunts and Gargoyles, immediately begin preparing for the assaults that are to come. Other strains begin to burrow deeper into the planet’s crust. These may include Mawlocs and Trygons. As these creatures burrow, they plant the spores that can later grow into Capillary Towers. Other organisms may use the tunnels these massive forms create to access a planet’s mineral wealth and subterranean life in the shelter of the tunnels. At the same time that this rain of devastation begins, those Genestealers and Lictors which have already infested the planet reveal themselves. Using the knowledge that they have obtained and the hybrid fauna they have spawned, these creatures sow confusion through the ranks of the defenders. By selectively targeting officers and communications hubs, the infiltrators can effectively delay or even compromise a planet’s defences. During this phase of the encroachment, a planet’s defenders must take rapid and decisive action or all hope may be lost. Cutting the attack off at its source is the optimal solution. If the hive ship can be destroyed, the remainder of the Tyranid fl eet may lose its cohesion, falling into confusion. This presents the defenders with an opportunity to divide and conquer the remaining forces. While less effective, destroying mycetic spores as they fall to the planet may also help the cause. Even the massive bulk of a hive ship has a limit to its resources. Each spore destroyed may mean greatly fewer organisms to face on the ground. The Tyranid hive mind possesses the ability to make a tactical assessment and modify its strategy. On admittedly rare occasions, a fleet facing unexpectedly stiff resistance may break off the assault and retreat to attack an alternative target. Countermeasures against Genestealers and their ilk are crucial to this stage. With astrotelepathy restricted, any additional loss of communications on the planet could quickly doom the defenders. Extensive security measures must be taken to preserve the integrity of all communication and command centres.
- Assault - Once the Tyranid forces have established a foothold on the planet’s surface, they quickly begin the process of eliminating any resistance. Endless swarms of the smaller breeds—including Gaunts, Gargoyles, and Genestealers—rampage through the skies, across the land, and under the oceans. Interspersed with these creatures, the larger biomorphs—including Carnifexes, Tyrannofexes, and even Hierophant bio-titans—accompany their smaller brethren, sowing endless destruction across the planet. These varied breeds come together in large hordes, that sweep forward to create battlefronts that may be hundreds of kilometres in length. Behind the battlefront, Capillary Towers, many thousands of metres in height, burst forth from the planet’s crust. These towers consolidate the biomass that the swarm has already absorbed, using it to breed additional organisms to assist in the assault. While the towers may appear to be a Tyranid plant analogue, they are no less aggressive than the more mobile forms. Capillary Towers extend tendrils throughout the planet that can absorb indigenous species—both plants and any small or slower moving organisms. As they do this, the towers also filter the planet’s atmosphere, absorbing the biomass of microbes and small flying creatures. Along the battlefront, Termagants use their ranged weapons to lay waste to opposition, while Hormagaunts boldly engage any opposition in close combat. These xenos, along with other variants of the Gaunt genus, may be found in swarms of hundreds coordinated by Tyranid Warriors. In those instances when sheer numbers prove inadequate to overcome the planet’s defences, the Hive Mind may direct larger strains to assist in the battles. For those planets with extensive defences, the swarm may grow exceptionally large creatures. Specimens of the Dominatrix and the Hierophant strains have been observed which are comparable in size and strength to Imperial Titans. In cases when a defensive point seems insurmountable, the Hive Mind is quick to adapt its strategy. In many cases, Raveners and Trygons may be used to burrow under defenders, attacking from behind or beneath enemy lines. In other cases, Shrikes or Harpies may make strafing runs from above. While the swarm will readily sacrifice thousands of biomorphs to take a single metre of ground, it will not waste them needlessly. Alternative strategies are consistently employed, as the Tyranids are clear masters of adaptation. It is worth noting that the battlefront swarms that cross the planet’s surface do not typically devour the planet’s defenders. Rather, they leave a swathe of refuse in their wake to be consumed by the next wave of organisms. This carpet of the dead may, of course, also include those Tyranid organisms that the defenders have managed to overcome. Their deaths hold little meaning to the Hive Mind. They have served their purpose, and will serve the swarm once more after their corpses are devoured. In the skies over the planet, Gargoyles and Harpies swarm in numbers large enough to block out the light of the system’s star. While they may assist in land-based battles, they also serve two additional purposes. Like the Capillary Towers, these flying organisms devour the biomass of the skies, returning it to the Tyranid swarm upon their deaths. They also serve to block out the sunlight from any photosynthetic life. Over time, this can have an effect on the planet’s atmosphere and climate as plant life is unable to synthesise oxygen. The only effective recourse at this stage of the invasion is all out war. By this stage, the invading forces have fi rmly established a presence on the target planet. Eliminating the hive ship would not avert the damage done. Further, depending upon the numbers and types of creatures on the surface, the Hive Mind might still persevere. Even if the Hive Mind were overcome and the majority of the xenos were eliminated, the battles to cleanse the planet completely could continue for millennia. The Tyranid taint extends to the microbial level, and all of these xenos are strongly resistant to biological and chemical toxins. Even the tiniest organism could have the potential to spawn more dangerous organisms given time and opportunity.
- Subjugation - Even as the more militant biomorphs continue to battle the planet’s defenders, others begin sweeping up behind them, collecting all available biomass. Some of the substrates collected are used to generate additional Tyranid creatures. In this manner, the planet’s natural resources are turned against it, providing additional tools for the swarm. The majority, however, is set aside to feed the hive ships orbiting the planet. Those massive creatures generally delay their feeding until after the planet has been secured. Near the battlefront, untold thousands of maggot-like Rippers are deployed from the sky to form massive, tightly packed swarms. With fang-filled jaws, they devour every organic substance they can find—living or dead. Once these abominations have eaten all they can, they slowly drag their bloated bodies towards digestive pools formed by the Capillary Towers. Rather than spewing the devoured biomass into the pools, the Rippers hurl themselves in, to be digested along with all that they devoured. New Rippers are continuously created to propagate the cycle of gluttony. As the planet’s surface is depleted, similar biomorphs deplete all of the life in the oceans and within the planet’s crust. Eel-like Rippers swarm through the oceans in massive swarms devouring all of the native sealife. Burrowing variants expand the tunnels dug by Trygons and Raveners, consuming subterranean fungus, root systems, and any burrowing fauna. Mineral reserves are also depleted, particularly rare ores that may be incorporated into the exoskeletons of the various biomorphs. Massive Capillary Towers develop in even the deepest parts of the planet’s oceans. These towers, which may stretch several kilometres up through the sea, are capable of withstanding the crushing pressures of the depths and thriving in even the coldest of waters. As they grow, they may even modify the planet’s tidal flow as their powerful metabolic filtration systems draw in all biomass. The only effective recourse at this stage is Exterminatus. Planets which have been subdued are no longer salvageable. The only hope for the Imperium is to destroy the feeding system before the biomass can be used to feed the fleet for further attacks. The one positive aspect is that at this stage, the Tyranid fleet may have expended their resources in preparation for the gluttony they expect as the planet’s biomass is absorbed. Attacking the voidfaring biomorphs and annihilating the planet may be easier than it would have been at an earlier stage of the invasion.
- Absorption - As the last of the system’s defenders fall, the Capillary Towers begin to feed biomass back to the hive ship and its escorts. The massive living vessels extend tendrils through the atmosphere which make contact with the Capillary Towers, as they grow to pierce the edges of the atmosphere. Biomass is drawn up the towers, through a combination of massive pumping organs and suction. Once the last of the defenders have fallen, the surviving creatures of the Tyranid hordes hurl themselves into the digestive pools near the Capillary Towers. Their bodies are broken down and devoured so that the biomass may be returned to the fleet to be recycled into new creatures for future conquests. Along with their biomass, their memories, genetic innovations, and the gene patterns of all of the planet’s life forms are also absorbed. After the last vestiges of life have been absorbed, the Capillary Towers begin to absorb the planet’s water systems. All of these liquids are transferred into the voidfaring organisms, some of which may grow dramatically in size as their storage vesicles expand to accommodate the newfound resources. As this happens, many of the Capillary Towers are also broken down so that their biomass may be reabsorbed. Finally, the planet’s atmosphere, and then the last few massive Capillary Towers are absorbed into hive ships. Some Magos Biologis theorise that this may require even more massive voidfaring Tyranids than those previously identified. Others postulate that the ships use previously unseen techniques to compress the atmosphere into a solid state. Though the precise mechanism is unknown to the Imperium, the outcome is certain: nothing is left behind but a barren, airless rock of little value. As it travels between systems, the Hive Mind analyses the new genetic patterns it has identifi ed. Some of these may be used to develop new biomorphs. Of course, these new strains may not appear immediately. The Hive Mind may save them for deployment at a time when a new strategy is required. Clearly, adaptation is a key factor in the Tyranids’ long-term success and survival. By this point, the battle is well and truly lost. Any defenders who arrive are far too late to save the planet. Their only possible hope is to spread word to neighbouring systems, in the hopes that they might arrive before the Tyranid threat. Attacking the voidfaring biomorphs immediately after they have fed is to attack them at the height of their power.
Tyranids appear in a multitude of genera, and all have an extremely rapid rate of evolution directed by the Hive Mind, adapting to threats in direct response to their presence. Tyranid matter is constantly reabsorbed into biomass reclamation pools to create new species and adapt existing ones to suit the Hive Mind's immediate purpose.
- Hive Tyrants are large and enormously strong Tyranids, who act as the leaders of the swarm and a synaptic conduit for the smaller creatures. They are highly psychic and highly mutable, and have a closer connection to the Hive Mind than most other genera of Tyranids. They are skilled at both close combat and ranged attack, more so than most other Tyranid organisms. Sometimes they are spawned with wings. Imperial Techno-Magi believe that Hive Tyrants are the repository of a Hive Fleet's collective consciousness, which means they completely embody the Hive Mind, yet their destruction does not in any way diminish its presence.
- Broodlords are another Tyranid synaptic organism, regarded as the epitome of the Genestealer breed. The Broodlord is one of the first Genestealers to make planetfall on a victim world. They are devastating in combat and are specifically adept at infiltration on the battlefield to get closer to the enemy. They are very adaptable and highly intelligent. Broodlords are also the center of Genestealer Cults, and they coordinate the cult's attacks. If the Broodlord is killed, then one of the purestrain Genestealers will eventually evolve into a new Broodlord after a period of time.
- Tyrant Guard are a special species of Tyranid spawned in small broods for the sole purpose of defending the Hive Tyrant. They are large, tough, and difficult to harm, and it is nearly impossible to surpass their defense. Tyrant Guard are completely blind, utterly controlled by the synapse creatures they protect. On occasion Carnifex also benefit from the Tyrant Guard's protection. Tyrant Guard are believed by some Adeptus Mechanicus Magi to contain the DNA of the defeated Space Marine Chapters, but the Imperium considers this blasphemy and denies its very likely possibility.
- Tyranid Warriors are synaptic foot troops for the swarm. In between the size of a Hive Tyrant and a Gaunt, they serve as psychic resonators and assist in guiding the lesser Tyranid troops into battle. They are fast and powerful, with the capability to be strong at ranged combat or in close quarters in a similar fashion to the Hive Tyrant.
- Lictors are large, deadly organisms bred for their stealthy qualities. A Lictor is basically chameleonic in nature, allowing it to blend with its surroundings to hunt and later kill its prey. Lictors are usually only seen when the Tyranids are springing a deadly ambush onto an unsuspecting army, unleashing a bio-engineered killing machine within their own ranks. They range ahead of the swarms, performing commando raids of sorts, and gathering information by devouring their victim's brains. The Lictors possess stealth and cunning of an unprecedented scale - to a point where they can best the famous Catachan fighters in jungle combat. Many Imperial Guard commanders have lost their troops in the shadows as they blink for a second; that is the terrifying undetectable Lictor at work.
- Gaunts are the basic staple combat unit of a Tyranid swarm. They are smaller and less physically powerful than most other Tyranid organisms, but they are extraordinarily adaptable and always attack in large numbers. They are a fully mutable species, and some are grown with extra wings, adrenaline/venom sacs, and even bizarre biomechanical weaponized symbiotes, including the dreaded spike rifle.
- Gargoyles are essentially winged variants of the Gaunt genus. They possess many similar traits, including a smaller size and physical prowess than most Tyranid organisms. Gargoyles retain most of the physical traits of Gaunts, however, and their lower legs have atrophied to little more than stumps. Like their cousin, the Gaunt, they are capable of being armed with a large host of biomechanical, symbiotic weaponry.
- Rippers are small, snake-like organisms designed to devour biomatter so that new DNA and nutrients can be absorbed by the Hive ships. They are released in the final stage of a Tyranid invasion.
- Genestealers are ferocious humanoid creatures, supposedly derived from human DNA, that are used as a vanguard to the Tyranid invasions of the Imperium. They infiltrate human societies, creating Genestealer Cults, as described under the tactics section above. They are also used as shock troops on the battlefield, where their sharp claws and instinctive close combat skills allow them to tear heavily armed opponents to shreds.
- Carnifexes – originally known as screamer-killers – are huge, hulking, living battering rams, armed with a variety of biomechanical, symbiotic weaponry. Even stronger than the Hive Tyrants, they are used for assaulting fortified positions and as armor formations, such as during boarding actions. Carnifexes are the Tyranid equivalent of tanks or Space Marine Dreadnoughts - and the monstrous creatures can be mutated into a multitude of different sub-species, some designed for tank hunting, others built to produce acid and toxins ideal for anti-infantry combat.
- Raveners appear to be related to both Rippers and Tyranid Warriors. These large beasts are designed for fast assaults against lighter enemies, and dig through the ground to perform surprise raids.
- Zoanthropes are a type of psychic artillery, whose highly evolved brains swell out of proportion with their bodies. Through their use of psychic powers they can perform a number of roles on the battlefield. Some evidence points to later incarnations of Zoanthropes being improved by the Hive Mind's assimilation of Eldar DNA following the Hive Fleet Kraken Tyranid assault on the Craftworld Iyanden.
- Biovores are sluggish, sessile creatures, whose only task is to grow and launch Spore Mines towards the enemy. The Spore Mines grow inside the Biovore's body, and are then hurled across the battlefield through a muscle spasm. Biovores are supposedly evolved from Orkish gene-stock.
- Bio-Titans are enormous organisms, evolved as a response to other races' Titans and other super-heavy warmachines. They are (as of yet) the largest land-based Tyranid creatures encountered. They range from nine to thirty metres tall, and can single-talonedly take out an entire squad of Space Marines.
- Norn-Queens are gargantuan organisms that are essentially biomechanical wombs that give birth to all of the other known Tyranid life forms. They can biochemically and genetically manipulate biomass in infinite ways to create new organisms to serve any function the Tyranid race requires. The Norn Queens are housed in huge rooms aboard the Hive Ships. Each room is hundreds of metres high, filled with a single Norn Queen.
- Dominatrixs are the Norn-Queen's link to the Tyranid ground forces. They are huge monsters, almost as large as a Bio-Titan and the stronger, more psychically-powerful female Hive Tyrant. They are symbiotically fused with a smaller (Warrior-sized) entity which acts as a psychic, synaptic link to the linked Norn-Queen aboard her ship.
- Trygons are powerful serpentine organisms that tunnel behind enemy lines. Towering over even a Carnifex, Trygons are one of the most powerful Tyranids breeds in existence. Trygons can also become synapse creatures to control other Tyranids. Trygons can lead a force of Tyranids known as a 'Tunnel Swarm'. This swarm is usually comprised of Lictors and Hormagaunts. The armour of a Trygon vibrates as it moves, thus creating a bio-electric current which can be released at will on a group of foes.
- Mawlocs are a subspecies of the Trygon. They are worm-like and blind, though they are incredibly agile despite their size. Their short claws are not suited for close combat, rather to tunnel efficiently under the battlefield, although they are by no means defenseless. They prefer to swallow their prey whole to be digested alive for several days. Despite being blind, the Mawloc can gather information of the surface through pressure waves since they can travel through solid and fluid objects below ground. When a Mawloc begins to home in on the enemy, severe tremors errupt on the surface, which can tell the Mawloc where its prey is with more accuracy. If the sound is regular and rhythmic, it is easier for the Mawloc to home in on. Even a heartbeat will tell it where its next meal is.
- The Hive Guard are charged with protecting Tyranid structures and are capable of unleashing salvo after salvo of intense firepower. Essentially gun-beasts, they are heavily armoured in a shell-like carapace and have a body designed to be a stable firing platform for the massive impaler cannon bonded to their forelimbs. Physically linked to the shard-beasts that comprise the ammunition of their cannons, Hive Guard can target enemies with unerring accuracy - even those who they cannot see because they can receive sensory impressions from the shard bests in mid-flight.
The Tyranids bear a great many similarities to the xenomorphs designed by H.R. Giger for the Aliens film series, such as their hive mentality, innate hostility and the appearance of a large number of the different bioforms.
- Wargame Tactics for Tyranids Tactics on using Tyranids in the Warhammer 40k game
- Codex: Blood Angels (5th Edition), pg. 17
- Codex: Eldar (4th Edition), pp. 52-53
- Codex: Imperial Guard (5th Edition), pp. 18, 23-24, 27
- Codex: Orks (4th Edition), pg. 29
- Codex: Space Marines (5th Edition), pp. 30-33, 40
- Codex: Space Wolves (5th Edition), pp. 19, 21
- Codex: Tau Empire (6th Edition), pg. 35
- Codex: Tyranids (6th Edition)
- Codex: Tyranids (5th Edition)
- Codex: Tyranids (4th Edition)
- Deathwatch: Achilus Assault (RPG), pp. 47-51
- Deathwatch: Core Rulebook (RPG), pp. 341-342
- Deathwatch: Mark of the Xenos (RPG), pp. 33-34
- Deathwatch: Know No Fear (RPG), pg. 11
- Deathwatch: The Jericho Reach (RPG), pp. 170-176
- Iyanden: A Codex: Eldar Supplement (E-Book), pp. 45-47
- Warhammer 40,000: Planetstrike (Supplement), pg. 30, 54, 57-59, 74-77
- Warhammer 40,000: Rulebook (6th Edition), pg. 175
- Warhammer 40,000: Rulebook (5th Edition), pg. 166
- Warhammer 40,000: Rulebook (4th Edition), pg. 163
- White Dwarf 362 (UK), "Liber Apocalyptica: Trygons", pg. 46
- White Dwarf 97 (UK), "The Ultra-Marines" pp. 40, 45
- Lone Wolves (Graphic Novel) by Dan Abnett and Karl Richardson
- Planetkill (Anthology) Edited by Nick Kyme and Lindsey Priestley
- Priest of Mars (Novel) by Graham McNeill
- Legends of the Space Marines (Anthology), "Orphans of the Kraken" by Richard Williams
- The Last Ditch (Novel) by Sandy Mitchell
- Warriors of Ultramar (Novel) by Graham McNeill
- Forgotten Fleets - The Spore of the Alien: Xenos Threats Exposed
- Dawn of War II (PC Game)