%% Images selected/replaced per Image Pickin' thread: http://tvtropes.org/pmwiki/posts.php?discussion=r6ttx4k1fdsvupiteszws6iu
%% Please do not change or replace without starting a new thread.
%%
[[quoteright:332:http://static.tvtropes.org/pmwiki/pub/images/Nidseverywhere.jpg]]
[[caption-width-right:332: Yes, that space bug ''is'' eating a tank.]]

->''"We must scour them from the stars before they do the same to us."''

The Tyranids are an extragalactic swarm of aliens that doesn't just overrun worlds, but [[HordeOfAlienLocusts consumes everything on them]] right down to the bedrock, including the oceans and air. Tyranids are more of a virus than a species, as they instinctively scan the DNA of what they eat and apply useful evolutionary upgrades to their swarms, ensuring that they only grow more deadly with each victory. Everything they use, from ranged weapons to spaceships, are [[OrganicTechnology symbiotic organisms]], to the extent that it can be hard to tell where a Tyranid "gun" ends and the creature carrying it begins.

Though the individual creatures in the Hive Fleets are little more than beasts, Tyranids are controlled via synapse creatures by the race's HiveMind, which is ''extremely'' intelligent. While the classic Tyranid strategy is to overwhelm their foes [[ZergRush with weight of numbers]], the swarms have also been seen to ambush armored columns in narrow passages that turned tanks into helpless sitting targets, employ burrowing organisms to launch surprise attacks behind enemy lines, or use winged creatures to sow discord and confusion. Of particular note are the specialized Tyranids known as Genestealers, who implant their DNA in victims that turns their children into [[HalfHumanHybrid Genestealer/Human hybrids]], who will eventually form a cult on their homeworld that undermines the planet's defenses while psychically summoning the swarm. Three Hive Fleets have been encountered thus far: Hive Fleet Behemoth nearly overran the Ultramarines' homeworld of Macragge and killed their entire 1st Company, Hive Fleet Kraken all but wiped out the Eldar of craftworld Iyanden, and Hive Fleet Leviathan is currently rampaging through an Ork empire... and these are likely just the vanguard of more Tyranid swarms still en route to the galaxy. The optimistic take on the Tyranids is that they are moving on our galaxy after cleansing one or more other galaxies of life. The pessimistic take is that they are running from something worse.

The tabletop Tyranid army is a mix of swarms of highly-expendable critters able to swamp even Imperial Guard or Ork forces, backed-up by lumbering monstrous creatures capable of tossing tanks around with their tusks or blowing up heads with psychic powers. They also contain units of specialist creatures able to infiltrate or move quickly in order to keep the enemy occupied in close combat while the rest of the army closes in, and the biomorph system allows units to be upgraded to deal with specific targets rather effectively. The Tyranids' two main weaknesses are comparatively few ranged units, as well as the reliance on a few synapse creatures to keep the swarm together. The latter is offset by the fact that the presence of said creatures makes the rest of the army fearless, and the former rarely comes into play as the standard Tyranid strategy is to roll over the enemy like a tsunami.

[[http://www.games-workshop.com/gws/catalog/productDetail.jsp?prodId=prod2340080a The most recent codex]] was released in January 2014.

----
!!Notable Tyranid tropes include:

[[foldercontrol]]

[[folder:Hive Fleets]]

* TwoDSpace: Averted with Hive Fleet Leviathan. The Imperium was perplexed by Tyranid attacks taking place far behind the "front line" at the galactic "east," until they realized that the Hive Fleet had ''flanked'' the galaxy and was attacking "upward" from "underneath" it.
* AbsurdlySharpClaws: Any 'nid strain from the genestealer on up is fully capable of cutting through PoweredArmor, and the larger monsters can open a tank like a sardine can.
* AcidPool: Digestion pools created and maintained by the Tyranids on invaded worlds. Tyranid organisms (especially ones which have been consuming the local environment) will throw themselves into the pools to be rendered down into biomass to be reabsorbed by the hive. Smaller digestion pools will eventually be drained by capillary tendrils through the ground to empty into a vast digestion ocean. This ocean will then have feeder tendrils dropped into it from hive ships from orbit, as a kind of temporary suction-based SpaceElevator to finally absorb the biomass back into the fleet.
* AdaptiveAbility: As part of their fluff, this is what makes the Tyranids so dangerous; they constantly mutate and evolve to counter any weapons or tactics brought to bear against them, as well as [[CannibalismSuperpower absorbing the genes of other lifeforms to increase their options]].
** However, this is also a weakness; in theory, a successfully strained Hive Fleet could be pushed so hard that they use up all of their harvested biomass faster than they can replenish it, and/or end up mutating into MasterOfNone strains in their quest to become JackOfAllTrades. This is exemplified by Hive Fleet Gorgon, the only canonical Hive Fleet to focus on the Tau, so far. Because the tau, unlike the Imperium, are constantly redefining and reinventing technology and tactics, Gorgon was pushed to extinction; unable to replenish its biomass as fast as it was depleted, and incapable of producing the larger, vital synapse creatures needed to control its smaller, more simple-minded spawn, the tau were able to whittle it down. The surprise addition of an Imperial Fleet, and a hasty, reluctant treaty between humans and tau, was the final nail in the coffin; now Gorgon was torn between directions to evolve in. Evolve to counter the tau, and be left vulnerable to the Imperium, and vice versa. It couldn't focus on one, so it was torn apart and eliminated.
** Prior editions hinted that every Tyranid lifeform encountered is an offshoot of one of the main races; Zoanthropes are born from Eldar, Biovores from Orks, the basic genestealer from humans and Tyrant Guards from [[spoiler:Space Marines]].
* AlienKudzu: As a Tyranid invasion of a world ramps up, self-replicating organisms are landed on a planet to begin initial biomass consumption, and to pump out both smaller scale creatures for scouting and undermining defenses, and to help [[{{Terraform}} render the rest of the world's biomass into a more easily edible form]].
* ApocalypseHow: Every planet they conquer gets a Class 6, and unless some way is found to break the Hive Mind, the same ''will'' happen to the entire Milky Way galaxy.
* ArtEvolution: Compared the Tyranid models from [[http://i5.photobucket.com/albums/y163/schepphimself/TyranidWarriors.jpg 2nd Edition]] with the ones from [[http://www.games-workshop.com/MEDIA_CustomProductCatalog/m490607_99120106003_TyranidWarriorsMain_445x319.jpg later editions]]. Earlier Tyranids had more biological variety too, until their redesign gave the race a more unified look, such as adding boney ridged crests on almost every head.
* AttackAnimal: The lesser Tyranid creatures qualify, having little independent intelligence and only minimal (though often brutal) instinct to guide them. However, they have "handlers" in the form of synapse creatures, which are both more individually intelligent and capable of interfacing with the HiveMind at greater distances, giving psychic "commands" to the lesser creatures as long as they remain nearby.
* BigBad: That HiveMind connection is the machine running all the cogs. Major representatives are Synapse creatures like Hive Tyrants, but those are simply cells in the overall brain of the HiveMind in general. The Imperium hopes to find ''something'' that directly controls the overall Hive Mind, so they can kill it and stop the Tyranids for good.
* BladeBelowTheShoulder: Type 3 for some Tyranid melee units, which have their arms below the elbow replaced with long [[SinisterScythe scythe-like]] talons, tapering down to [[AbsurdlySharpBlade a monomolecular edge]] like most of the blades in this setting. Note that older editions also had some units in which a bone-like blade was simply gripped in hand in the manner of a sword (and the Swarmlord special character still does this) but ArtEvolution has merged most of these weapons into their wielder, putting them into this trope.
* BrainFood: Any Tyranid creature with lamprey-like feeder tendrils in place of a mouth will be likely to eat brains. Lictors in particular are known for doing this, as it allows them to sift though a consumed organism's memories for information. This is part of a Lictor's role as a vanguard organism, helping the Hive Fleet gain intelligence on what worlds would be good targets for consumption and what kind of defenses to expect.
* BreathWeapon: Some critters can make bio-plasma attacks, vomiting up a blast of white-hot energy accompanied by a piercing screech.
* BugWar: If your Tyranid problem has gotten beyond the Genestealer Cult stage, [[EndOfTheWorldAsWeKnowIt you're pretty much screwed]].
* BulletSeed: A near-literal case with many of the more rapid-firing {{Living Weapon}}s wielded by some Tyranid organisms. Except that the "seeds" are things like tiny beetles which bore into flesh, or little worms which secrete acid and melt themselves into a target.
** In one literal case, the Tyrannofex has the Rupture Cannon which fires two rounds: a bloated tick... and a seed case. Fluff says the two react in a catastrophic fashion when their chemical fluids are mixed upon impact.
** Another literal one is the Barbed Strangler/Stranglethorn Cannon. It fires a seed pod that sprouts into a mass of fleshy tentacles in an instant, strangling whatever is within it's reach. It has immense strength, but poor armor penetration because stronger armor can simply shrug off it's attempts.
* ChestBlaster: An option for some offensive biomorphs. Tyranid models will occasionally mount flesh-hooks or devourers underneath some folds on their underside between their forelimbs.
* CombatTentacles: Ranging from lash whips and flesh hooks on the battlefield creatures to tentacles on ''spaceships'' for boarding actions.
* CompositeCharacter: Imagine a merge of the [[Franchise/{{Alien}} Xenomorphs]] and the [[Film/StarshipTroopers Arachnids]]. [[OhCrap You may weep now]].
* DoesThisRemindYouOfAnything: Tyranid ranged weapons feature a lot of [[{{Squick}} sphincters and muscle spasms ejecting spurts of hot liquids]].
* EatingOptional: Most Tyranid organisms don't actually have a functioning digestive system, as they're bio-engineered killing machines and such a thing would take space and energy away from muscles, reinforced endo- and exoskeletons, weapon-biomorphs etc. If they aren't killed by the enemy first, they will eventually starve to death. Many of them still have instinctive behaviour to feed, though, as it makes them attack the enemy even when not under control of the synapse creatures. The Ripper swarms are the most obvious example, as their whole purpose is to eat any biomass they come across in order to transport it to the reclamation pools to be digested and fed to the Tyranid hive ships.
** Averted with a new unit in 2014, the Haruspex, which is specifically designed to eat everything in its path as part of the Hive Mind's strategy to consume as much biomass as possible.
* EmpathicWeapon: In a quite literal way. The {{Living Weapon}}s employed by the smaller Tyranid genus types symbiotically bond with their wielder, melding their flesh together and growing spinal-like attachments to mesh their nervous systems together. In this way, the weapon itself acts as a sort of secondary "brain" for the creature, giving the limited intellect of its primary brain the knowledge and skill necessary to use the weapon.
** Taken to extremes with the Pyrovore; the weapon is sentient but the body is not.
** See also the new Exocrine, which is essentially a big walking weapons platform for an organic artillery canon.
* EverythingsBetterWithDinosaurs: The big ones are often described as dinosaurs.
* EvilEvolves: Characteristic of the Tyranids is that they evolve and [[AdaptiveAbility adapt to overcome stubborn resistance]]. Some of these adaptations are taken from [[PlanetEater consuming worlds]], where the Norn Queens in the fleet [[LegoGenetics sift through the collected genetic data looking for useful characteristics]] to incorporate into future generations. Others are adaptations that occur in the field, allowing the swarm to overcome specific difficulties by targeted mutation. Such evolution, though, inevitably tends to result in some NecessaryDrawback weakening them in one regard while it strengthens them in another. As the smaller creatures have a much shorter lifecycle and gestation time, a hive fleet that is heavily adapting will tend to be composed of a [[ZergRush greater proportion of smaller units]], leaving a shortage of [[HiveQueen synapse creatures]]. This can become a potential weak link in their force structure, which is why not all hive fleets take that approach.
* {{Expy}}: In many ways, especially with the overall design of Genestealers and [[http://img3.wikia.nocookie.net/__cb20121023045459/warhammer40k/images/3/3b/Norn_Queen_Concept_2.jpg this concept art depicting a Norn Queen]], the Tyranids are [[SincerestFormOfFlattery practically a walking tribute to]] [[Franchise/{{Alien}} the Xenomorph]] designed by Creator/HRGiger.
* ExtremeOmnivore: The Hive Fleets leave nothing but lifeless, airless rocks in their wake.
* FlechetteStorm: Spinefists, one of the Tyranid's many SpikeShooter type weapons. [[DualWielding They are always wielded in pairs]], and [[BlowGun use compressed air built up from the wielding creature's own lungs]] to propel the spines. This means that the larger creatures with greater lung capacity can [[MoreDakka fire spines substantially quicker]].
* FragileSpeedster
** Hormagaunts are a Tyranid species meant to swamp the enemy in close combat, and to accomplish that they are bred to be very, very fast and agile. However, they are also quite frail, which is why the Tyranids [[ZergRush send them in great numbers at once]]...
** As Tyranids do not rely on conventional Grav-Tech to gain flight or have powerful engines, they instead have to resort to good ol' hollow bones and wings for their fliers. Unsurprisingly Gargoyles, Harpies and flying Warriors tend to have weaker armor than their ground-based counterparts, representing how fragile they can be. Tyrants subvert this somewhat, as they are able to project a psychic field around them that's just as durable as armor, making them [[LightningBruiser Lightning Bruisers]] as a result.
** Surprisingly averted with the massive Hierophant Biotitan. Its stalky legs and exposed bone structure looks fragile, but the thing is shockingly fast and incredibly durable, enough that it can stand toe-to-toe with a ''Reaver Titan'' in combat.
** The Tyranids as a whole have seen a shift into this with the 5th Edition; many of the unit choices are more expensive with little to no help with their survivability. However, the moment they get withing reaching distance of you, they will tear you to shreds, and they have many methods of closing the gap ''fast''.
* GiantEqualsInvincible: Or they might as well, as far as Tyranid [[{{Kaiju}} bio-titans]] are concerned. With [[DeflectorShields warp fields]], [[HealingFactor rapid regeneration]], and [[DeadlyGas neuro-toxic spore emissions]], it generally takes something like a [[HumongousMecha Titan]] to fell one of these gargantuan beasts.
* HealingFactor: Rapid regeneration was introduced by the unique Carnifex named "Old One Eye," and is now a standard upgrade for most Tyranid organisms.
* HiveMind: Chief Librarian Tigurius of the Ultramarines has made psychic contact with it, and could only describe "an immortal hunger."
** And he's the lucky one, as every other psyker who tried to make contact either went insane or died. It's theorized you'd need a human psyker on the same level as the Emperor.
* HiveQueen: Synapse creatures, though only the rarely seen Norn Queens are female. Probably.
* HollywoodTactics: Averted. They may 'look' like dumb animals, and use superior numbers, but the Hive Mind is a tactical and strategic super-genius.
* HordeOfAlienLocusts: After the invasion, they even "recycle" their own soldiers, living and dead.
* ImprobableAimingSkills: The Hive Guard, a heavily armored feeder tendril guardian, wields an [[ImpaledWithExtremePrejudice Impaler Canon]], a weapon which fires long spikes with membranous fletching at extreme velocity. The Hive Guard in fact [[EyelessFace has no eyes]], but "sees" through other members of the swarm, allowing it far greater situational awareness than it would otherwise have. Further, the spikes themselves possess a rudimentary awareness, flexing their fletching membranes in flight to adjust their trajectory and further ensure a target is hit, even from extreme range and in bad conditions.
* ItCanThink: The larger "synapse" Tyranid creatures certainly can. However, these creatures take more time and biomass to develop than the smaller ones, and thus there tend to be fewer of them, while the others must make do with more animalistic intelligence. However, as long as smaller creatures remain near the bigger ones, they can benefit from its intelligence thanks to their HiveMind.
* [[ItsRainingMen It's Raining Tyranids]] -
** Tyranids typically arrive on a planet's surface via "mycetic spores" dropped from space, especially the larger creatures which take more time to mature. Smaller ones are typically born "in the field" via the [[AlienKudzu consumption of the local environment]].
** Tyranid Gargoyles are variations on the gaunt genus with wings to carry them aloft. Their role is to [[DeathFromAbove swoop down on enemies from above]] and keep them occupied while larger creatures move into position. When Gargoyles have to move long distances, they will accompany a larger, [[OurDragonsAreDifferent dragon-like]] flier called a Harridan, clinging to its underside to save on their own energy.
* TheJuggernaut: This is the function of the Carnifex unit. It acts as a line breaker, plodding forward implacably as attacks waste themselves against its exceptionally dense carapace, cutting down or bowling over anything that stands in its path like a living battering-ram.
* KrakenAndLeviathan: The bigger hive ships are this of the SpaceWhale variety. Also forms an [[AnimalThemeNaming Animal]] and [[ReligiousAndMythologicalThemeNaming Mythological]] ThemeNaming scheme for the hive fleets.
* LargeAndInCharge: Larger Tyranid organisms are more likely to be the synapse creatures directing the swarm, leading to the Imperium's official policy on combating them: shoot the big ones.
* LivingGasbag: Tyranid spore mines are these, with jellyfish-like tentacles hanging below them and thin but rigid series of small overlapping chitinous plates surrounding its float-bladder. The Tyranids launch them from the biovore species to float over the battlefield and find targets. They tend to end up hovering just above the ground and have limited locomotion, but when a non-Tyranid draws near them [[ActionBomb they explode]], the sharp pieces of their shell scything out like shrapnel and spreading toxic spores and caustic fluid as they do so.
* LivingShip: The Hive Fleets, complete with [[WombLevel disturbingly fleshy interiors]].
* LivingWeapon:
** The Tyranid units themselves are these, as they are explicitly bred as living combat tools.
** To a more specific degree, the weapons used by smaller Tyranid units symbiotically bond with their wielders into a single organism.
* MasterSwordsman: Hive Tyrants, of swords made out of razor-sharp-bone with a psychic brain at its base yes, but still [[MasterSwordsman swordsmen nevertheless]]. The Swarmlord cranks this up to absolutely ludicrous degrees, weilding FOUR such swords at the same-time, and so blindingly fast with them that a virtually impenetrable wall-of-blades is what your sword will clash into if you try to fight it hand-to-claw.
* MeaningfulName[=/=]NamesToRunAwayFromReallyFast[=/=]RedBaron: Not for nothing were the Tyranids nicknamed "the Great Devourer". Whole planets are left completely lifeless of any and all biomass and minerals that could be useful. Just giant rocks spinning in the void.
** The Swarmlord, hive tyrant, tyrant guard, Red Terror, brood lord, Old One Eye, Death Leaper and the infamous carnifex all get a special mention. Even names that don't have obvious meanings, like the trygon, sound ominous.
* MookMaker: Tyranid hive ships, for starters, making every smaller creature and even other hive ships themselves. Below that, Tyranids seed invaded worlds with brood nests, which consume the local resources brought to them and churn out smaller creatures on-site, allowing them to change their force composition in the field. And taking this one step further, some Tyranid creatures themselves are walking (or crawling or slithering) {{Mook Maker}}s themselves, such as the Tervigon, which spawns Termagaunts from various womb-pustules on its belly while on the battlefield.
* MoreTeethThanTheOsmondFamily: Though some critters mix things up with feeder tendrils.
* MultiArmedAndDangerous: All the Tyranids are evolutions from a basic six-limbed shape, and most use all of them, except for some like the serpentine Raveners and the winged Gargoyle who have a pair of vestigial legs.
* MyBrainIsBig: Zoanthropes have always had huge heads, the better to channel psychic power. Models from earlier editions had torsos, arms, and legs, and would stand and walk on the ground. ArtEvolution has pushed later models into being little ''besides'' a brain, with a long, snake-like body to house its brainstem. It now uses [[PowerFloats its psychic power to levitate]] over the battlefield, rather than walk.
* NamedAfterTheirPlanet: While not named after their home planet (as no one really knows where the Hive Fleets come from) they are named after the first world that they made contact with the Imperium; Tyran.
* OffscreenTeleportation: They are never actually witnessed using any kind of faster-than-light travel and there's no evidence they have any, but their fleets move between stars as fast as everyone elses.
* OnlyKnownByTheirNickname: This applies to the few special characters the Tyranids have (see below), because they don't have names or identities as humans do.
* OrganicTechnology: It's interesting looking back over the model range to see how what once were distinct weapons became fused to their wielders.
* PlanetEater: They consume entire biospheres, leaving only an airless, infertile sphere of bedrock behind.
* PowerFloats: Zoanthropes do not even have legs, they just hover along via psychic levitation.
* PsychicStatic: One of the most dangerous aspects of the Tyranids is how the Hive Mind casts a "shadow in the Warp" ahead of it, which is strong enough to [[YourHeadASplode overwhelm any psykers]] on a planet targeted by the Hive Fleets. This is very bad news, since psykers are required for astropathic communication and navigation, which means when the 'nids are on their way, there's no chance of sending a call for help, and no way for it to arrive. Some Imperial scholars believe that the cause of this is the absolutely ''massive'' amount of psychic "bandwidth" that the Hive Mind requires, simply drowning out all other psychic voices in the area.
* PuppeteerParasite: The Cortex Leech, a little-known ripper genus. It's a small, fast-moving creature which leaps up to a victim's face, then extends flexible antenna into the victim's [[OrificeInvasion mouth, nose, ears]], and {{eye| scream}}s. These feelers burrow into the brain, and turn the victim into a drooling puppet of the HiveMind.
* {{Reincarnation}}: As of 5th edition, Hive Tyrants are unique in that they have distinct consciousnesses and personalities, which help them be more effective "generals." As part of the Hive Mind they can never be killed, meaning that if you destroy a Hive Tyrant in one battle, the next time you meet he'll remember your tricks, ''and'' he'll be pissed. The new special character The Swarmlord is believed to have involved in every major Tyranid conquest in their history in this way.
** The Swarmlord is a special character when compared to the other Hive Tyrants in the fact it is uniquely separate from the Hive Mind. Think of it as a very dangerous second opinion brought in only when the Hive Mind's usual strategies[[note]]'strategies' and not tactics, as the Tyranids constantly mutate and experiment to ensure tactical efficiency[[/note]] do not work on the foe it is currently fighting. What makes it unique is that while there are many Hive Tyrants, it's implied that there is only one Swarmlord at any given time, having its consciousness beamed across star systems on an as-needed basis. It's the sole Hive Tyrant that is not bound to any one hive fleet or ship.
* SandWorm: The Tyranids have something close, in the form of the Mawloc, a worm-like Tyranid with six powerful burrowing limbs alongside a long, chitin-plated serpentine body ending in a wicked earwig-like tail. Much like the classic trope inspiration, they are almost entirely blind and rely on sensation of vibration through the ground. Even a person standing stock still can be detected by a Mawloc, if their terrified heart is beating loud enough...
* ShooOutTheNewGuy: Due to legal reasons, the Doom of Malan'tai and Parasite of Mortrex don't have rules anymore.
* SpikesOfVillainy / TheSpiny: Tyranid creatures are almost universally covered in chitinous spikes and sharp edges. As one Games Workshop player once said in a battle report:
--> ''You can talk all you want about strategy and unit choice, but [[WhenAllYouHaveIsAHammer when it comes down to it]], all Tyranid tactics end up as "spiky death".''
* SpikeShooter: Stinger Salvos, Cluster Spines, Impaler Canons; the Tyranids are not short of variations on these.
* StarScraper: Capillary towers are an ''organic'' version of these. As the ecological transformation of a Tyranid invasion begins to reach a "critical" stage, these begin to grow out of the accumulated biomass and rich minerals that the invasion has been rendering down into [[AcidPool digestion oceans]]. They gradually grow to a height of several kilometers, and act as an anchor point for hive ships, who extend feeding tendrils down to latch onto them and draw up the rendered biomass through them, like drinking up the biosphere through a giant straw.
* [[TheSwarm Swarm Of Rippers]]: The "ripper" genus is a family of many kinds of small Tyranid organisms which primarily exist to gather biomass for the swarm. They are weak and possess little offensive ability on their own, so they are typically only deployed after resistance has been cleared out to consume passive prey. Their quick-breeding allows them to multiply in numbers such that they form a rolling "wave" of living creatures that leave only desolation in their wake. A defender should hope that they were killed by one of the larger creatures as opposed to simply wounded [[EatenAlive by the time the rippers get to their body...]]
* TentacleRope: Tyranid flesh-hooks are a variation of these, except instead of lashing around a foe, they ''dig a boney meat-hook into them''. They also function as a [[GrapplingHookPistol Grappling Hook Launcher]] for scaling obstructions.
* ThemeNaming: Many Tyranids are named after relatively obscure words for unpleasant and domineering women: harridan, termagant (and its older form, Tervigant, when it referred to a pagan god that medieval Christians believed Muslims worshiped), harpy, and dominatrix, though many of these are also puns or references - termagants were a type of ground unit from the 1970s Metagaming game ''Chitin: 1 The Harvest Wars'', and harpies are, of course, a type of mythological flying beast.
* TunnelKing:
** The Tyranid Ravener is a slithering creature capable of tunneling under the surface to bypass static defenses and literally undermine entrenched positions. For high value and seriously hardened targets, groups of Raveners will often be lead by a Trygon, their far-larger cousin.
** Now with even greater emphasis on tunneling comes the Mawloc. These things are like [[Film/{{Tremors}} Graboids]] turned UpToEleven.
* [[{{Terraform}} Tyranoform]]: The effect [[AlienKudzu Tyranids have on planets they invade]], pre-consumption, involves some rather unpleasant alterations to the existing biosphere. This serves to "tenderize" the planet, making the biomass easier to process and consume when the hive fleet moves in after the defenses have been neutralized.
* TheVirus: Or more precisely, The Bacterial Microbe. Several of the initial Mycetic Spores launched during a Tyranid invasion release these microbes around their point of impact. The microbes potentially infect nearby lifeforms, causing mutation, death, and rapid decomposition. This in turn grows into colonies of brood nests to birth more Tyranids, and jutting spore chimneys which spout more of these microbes into the air to let the wind carry them elsewhere. Eventually, [[AlienKudzu all native life is choked out by this process]] and the world becomes a wasteland of digestive pools and vein-like bio-mass capillaries.
* WeHaveReserves: ... that outnumber the stars.
* YouAreWhoYouEat: The Tyranid can make use of the genetic code of the worlds they consume. For instance, the Zoanthrope "Doom of Malan'tai" got it's name and extra psychic power from eating a bunch of Eldar ''souls.''
* ZergRush: They even [[TropeMakers inspired]] the trope namer!
[[/folder]]

[[folder: Genestealers]]
[[quoteright:300:http://static.tvtropes.org/pmwiki/pub/images/genestealer_cult_8924.jpg]]
[[caption-width-right:300:Genestealers (behind) with a Genestealer Cult (foreground).]]

Vanguard organisms of the Hive Fleets, Genestealers are deployed well ahead of the fleet's advance to undermine potential prey worlds. Because of this mission, Genestealers are bred to be much more independent than the Hive Fleets, a Genestealer brood being almost a separate hive intelligence unto itself. Capable of hibernating in wait for centuries, Genestealers were likely by far the first Tyranid organisms in our galaxy, their numbers maintained and expanded via their parasitic preying on other species for reproduction. With great strength packed into a compact body and claws capable of rending through even the toughest armor, Genestealers are deadly whether they are acting subtle or overt.

* AbsurdlySharpClaws: Genestealer claws are Absurdly Sharp, even by the standards of the setting, and the muscles on their limbs are much more powerful than they look. Stories abound about Genestealers able to rip open the armor of a Space Marine Terminator like it was a tin can (though in practice the Genestealer can only do that if it gets a really lucky grip on the victim.)
* AliensMadeThemDoIt: Literally in the case of those subjected to the [[FaceFullOfAlienWingWong Genestealer's Kiss]]. Their altered hormones will drive them to find a partner to mate with and produce offspring. Said offspring will incorporate the genetic code of the Genestealer who administered the kiss and will be [[MixAndMatchCritters horribly misshapen hybrids of the two species]].
* AssimilationPlot: The modus operandi of a Genestealer {{cult}}, though [[DownplayedTrope downplayed]] to the extent that they do not necessarily want to get ''everyone'' in. The early stages of a Genestealer population infiltration will have the brood lurk around the outskirts of society, careful to avoid detection and "[[FaceFullOfAlienWingWong kissing]]" a few lone individuals who will not be missed. As the cult adds new generations and grows in size, they will start fronts to allow them more freedom of movement and resources, becoming more selective as they go about who they bring into the "family" to groom themselves for more influence and avoid discovery. Eventually as a Hive Fleet approaches, they are driven to be more aggressive and will try to stage a coup, which may or may not be successful, but either way will divert attention and resources away from the oncoming threat.
* BreedingCult: The goal of Genestealer cults being to propagate more Genestealers in secret, gathering higher influence to better hide their growing numbers.
* {{Cult}}: When Genestealers infiltrate a population, they will go underground and look for isolated victims to "[[FaceFullOfAlienWingWong kiss]]". These individuals will reproduce [[HalfHumanHybrid Genestealer Hybrids]] and love them like their own. In order to maintain their "family" they will often find some kind of front or cover story to keep the nature of their children concealed. Such will usually adopt certain aspects of the host culture, twisting it around to center about the Genestealers, creating a secretive sect devoted to spreading their seed.
* DestinedBystander: The Genestealers were introduced early into the setting as a small piece of background lore. Once the Tyranids arrived, their role in the narrative was greatly expanded as being early elements of the Hive Fleet seeded into our galaxy. This was most likely a {{Revision}}, which involved a few minor {{Retcon}}s which relegated [[CharacterizationMarchesOn the original Genestealer conception]] with a minor offshoot of the race as a whole.
* FaceFullOfAlienWingWong: Genestealers reproduce via the "Genestealer's Kiss", an injection of their genetic material into a target via a long, diamond-hard "tongue." [[DependingOnTheWriter Depending on which bit of fluff you read]], this is either via a literal, face-biting parody of a kiss, or a slightly less {{Squick}}y injection into the torso, under the ribcage. The CiaphasCain novels use the latter method.
* GhostShip: The Hive Fleets are fond of leaving first generation Genestealer broods on Space Hulks, where they will go dormant and wait. Eventually the Space Hulk will arrive in a populated system, or it will be investigated by explorers, and there the brood will find their hosts...
* HalfHumanHybrid[=/=]NonhumanHumanoidHybrid: Half any-sentient-species hybrid. Genestealers have a curious reproductive cycle, where only a few early broods are birthed directly by the Hive Fleets, and all later members of the brood are born to host species that the Genestealers prey on. After infecting a host organism, that organism will be driven to reproduce, but any such offspring will be half the host species and half Genestealer. Naturally, such a creature is usually very misshapen as it [[MixAndMatchCritters combines traits of both species freely]]. However, later generations of hybrids will look progressively more like the host species, until by about the fifth or six generation they are completely indistinguishable from them. The children of ''that'' generation will then be more "pure" Genestealers and the cycle begins again.
* HiveMind: Like the Hive Fleets, the Genestealers have a hive mind. This mind is generally independent of the Hive Fleet, and is specific to particular broods, which is necessary considering that they often operate far from any other Tyranid organism and thus need to better think for themselves. However, when the Hive Fleets are inevitably drawn to a location where Genestealers have been reproducing successfully, those Genestealers will begin to become affected by the Hive Mind of the fleet, and will be spurred into more overt and aggressive action against their host populations. By the time the Hive Fleet arrives, the Genestealer brood will have been mentally re-absorbed into the Hive Mind of the fleet and function as their elite shock troops when overcoming its defense.
* HypnoticEyes: A characteristic of Genestealers is an ability to pacify potential prey by maintaining eye contact and moving slowly, though how much use this gets is heavily [[DependingOnTheWriter Dependent On The Writer]].
* MixAndMatchCritters: Genestealer hybrids, particularly first-generation ones, will mix an equal amount of characteristics from the genestealer and the host species. Later generations will [[DownplayedTrope downplay]] the Genestealer traits further with each generation, until around the fifth or sixth generation purestrain Genestealers are born to them.
* TheMole: Genestealer cults fill this role on a strategic level for the Tyranid Hive Fleets.
* MultiArmedAndDangerous: As per the other Tyranid creatures, Genestealers have six limbs. Two for standing upright, two for fine manipulation, and two as [[AbsurdlySharpClaws rending claws]].
* OurVampiresAreDifferent: The first recorded contact with Genestealers came from the moons of the planet Ymgarl. Originally though to be native to there, it was only later revealed that they were a specific mutation of the wider Genestealer secies and a vanguard of the Tyranids. Instead of the maw found on other Genestealers, they have lamprey-like feeder tendrils that they use to drain blood of victims. They are able to conceal themselves with limited [[VoluntaryShapeShifter shape-shifting]] abilities, but this requires them to feed often to maintain. Though their shape shifting is powerful, the Hive Fleets display no desire to re-absorb them, leading to speculation that the mutation might be unstable if assimilated back into the hive.
* ParanoiaFuel: {{Invoked|Trope}} by the Genestealers. Their infiltration of planets has the primary effect of destabilizing them militarily from within so they cannot effectively mount a defense, but secondarily by making it difficult for the planetary authorities to conclusively determine which individuals have been subverted by the Genestealers or not, continuing to make it difficult to mount a unified defense as the population and chain of command falls into a pattern of distrust and fear.
* ThePatriarch: The actual title of the first Genestealer to found a brood among a host species. As the brood of hybrids grow, the Patriarch will slowly grow progressively [[LargeAndInCharge larger and more physically powerful]]. By the time the forth generation of hybrids comes about and new Genestealers are being born, the Patriarch will be a massive beast. As every member of the brood is psychically connected with the Patriarch, the more the brood grows in number the more the Patriarch's psychic potential grows to accommodate them, eventually becoming a fantastically powerful psyker in its own right.
* PowerCreepPowerSeep: Possibly moreso than any other specific example in [=40K=], the power of a Broodlord as a psyker. In the fluff he's a supernatural powerhouse rivaling even the best Space Marine Librarians, as strong in the ways of the Warp as he is with his claws and muscles. On the tabletop he's one of the weakest psykers available to ''any'' faction (level one, with only one actual power he can use).
* PuppeteerParasite: The "[[FaceFullOfAlienWingWong Genestealer's Kiss]]" initially causes confusion and amnesia in the host organism, which renders them placid and can take several hours to resolve fully. However, after that time it brings the host under the thrall of the Genestealer brood, altering their hormones and perceptions so that they come to love the Genestealers and any children they have by them. Some puppets may not even realize that they are being influenced by an external intelligence.
* PutOnABus:
** Genestealer cultists haven't been playable units since 2nd edition, and perhaps a 3rd edition unit in White Dwarf.
** The Ymgarl Genestealers became a "special character unit" in 5th edition's codex, but were removed in the 6th edition codex.
* XMeetsY: Genestealer cults are ''Film/{{Alien}}'' meets ''Literature/TheShadowOverInnsmouth''.
[[/folder]]

[[folder: Notable Beasts]]
Although one would argue that a HiveMind race like the Tyranids shouldn't have special characters -- indeed, on a meta-level, this argument resulted in their lacking any in their fourth edition codex -- the Tyranids have always had unique units, beginning with the Red Terror and Old One Eye in third edition, then adding more in their fifth and sixth edition codexes.

!!The Red Terror
[[quoteright:250:http://static.tvtropes.org/pmwiki/pub/images/red_terror_250_4956.png]]

A blood-red Ravener-like monster that was responsible for terrorizing the Imperial miners of Devlan Prime for 20 days and nights, burrowing through the solid rockcrete with its six curving blade-limbs and devouring victims whole before vanishing once more. The Imperium has no idea what happened to it after that sighting.

* LegacyCharacter: On a meta-level. Raveners gained their ability to Deep Strike -- flavored in-game as them burrowing up from below to attack their foes -- and Trygons & Mawlocs gained their existence from this creature, who was originally the only one who could do it. Perhaps in homage, his entry in the 2014 codex notes that some Imperial scholars have suggested that the Red Terror may actually have been the first ever documented sighting of a Trygon and/or Mawloc.
* ParanoiaFuel: InUniverse. What ''was'' the Red Terror? And what happened to it after Devlan Prime? Was it destroyed? Was it reassimilated and used to churn out the Trygons and/or Mawlocs? Or is it still out there, killing, and the Imperium doesn't know about it because nobody else has ever survived an encounter with it?
* PutOnABus: Like Old One Eye, the Red Terror was removed as a playable model in the 4th edition codex, under the logic that a HiveMind race shouldn't have special characters.
** TheBusCameBack: But not until the 6th edition codex, whereas Old One Eye came back in the 5th edition one.
* SwallowedWhole: Has the ability to do this, both in the background text and on the tabletop.

!!Old One Eye
[[quoteright:350:http://static.tvtropes.org/pmwiki/pub/images/rsz_1oldoneeye_3226.jpg]]

A monstrous Carnifex that spearheaded the Tyranid assault on Calth, with the aid of its at-the-time unique healing abilities and bioweapons, only to be brought down by some brave Imperial hero, who seemingly killed it with a direct hit from a plasma pistol to the eye. Decades later, a band of smugglers found its frozen corpse and dug it out, hoping to sell it and be rich, only for the Carnifex to regenerate its wounds and resume to stalking the battlefields, somehow escaping Calth to bring death to the rest of the galaxy.

* AxeCrazy: Even by Carnifex standards, Old One Eye is a frothing mad berserker.
* EyeScream: Got shot in the ''eye'' with a ''plasma pistol''.
* GiantEnemyCrab: Kind of invokes this image, thanks to its crab-like pincered limbs.
* HealingFactor: Infamous for it, InUniverse. In the third edition codex, it was the only Tyranid that could regenerate, whilst when it reappeared in the fifth edition codex, it had a version that worked more effectively than those of other Tyranids with the Regeneration biomorph, though it lost this in the 2014 codex.
* LegacyCharacter: On a meta-level. Old One Eye's ability to regenerate and its unique crab-like crushing claws became standardly available biomorphs in all subsequent editions.
* PutOnABus: Old One Eye was removed as a playable model in the 4th edition codex, under the logic that a HiveMind race shouldn't have special characters.
** TheBusCameBack: Was restored in the 5th edition codex and has been playable since.
* WoundThatWillNotHeal: The empty eye-socket and exposed skull-patch from its first "death" is seemingly the only thing it can't regenerate.

!!The Swarmlord
[[quoteright:300:http://static.tvtropes.org/pmwiki/pub/images/rsz_1tyranidswarmlord_8234.png]]

The closest thing that the Swarm has to a true face, the Swarmlord is an ancient and incredibly powerful Hive Tyrant that is brought into being whenever the Hive Mind requires a greater level of tactical wealth and raw leadership than an ordinary Hive Tyrant can provide. If the Swarmlord dies, it is simply reincarnated again, and in this way it can be summoned to the aid of any hivefleet that ever needs its aid.

* BadassGrandpa: The Swarmlord is the oldest known living entity in the hivefleets, being implied to have been fighting since at least ''the last galaxy'' the Tyranids fought against.
* BigBad: Or at least, the closest to the concept that we can understand.
* CoolSword: Four unique serrated blades of organic bone/chitin sculpted around living crystals from outside of the galaxy in which the game is set.
* DualWielding: Taken UpToEleven in that the Swarmlord ''quadwields'' its bone-sabers.
* HiveQueen: Zigzagged. It does have a greater level of individuality than any normal Tyranid, and it is created when the Tyranids need more direct control, knowledge and purpose than the Hive Mind can give. However, it is still merely an aspect of the Hive Mind, not the actual leader of the Tyranid race, and so killing it does nothing more than killing any other synapse creature.
* ImplausibleFencingPowers: His swordplay is so good that he gets an ''invulnerable save'' against shooting attacks! Such a save is normally reserved for force fields, either made of technology or dark magic.
* MagicKnight: A powerful psyker and also very capable of curbstomping just about anything that gets into melee with it.
* NeverFoundTheBody: After the destruction of Hive Fleet Behemoth at the Battle of Macragge, the Swarmlord's body was never located. It's appeared on several battlefields afterwards, but its unknown if it was killed and reincarnated, or simply managed to escape.
* ResurrectiveImmortality: The Swarmlord can be killed, but its mind is just absorbed back into the Hive Mind, which can then recreate it whenever and wherever it is needed.

!!The Doom of Malan'tai
%%[[quoteright:150:http://static.tvtropes.org/pmwiki/pub/images/wh40k_doom_of_malantai_5814.jpg]]

A mutant Zoanthrope who was instrumental in the destruction of the Eldar Craftworld Malan'tai, by sneaking into the Infinity Circuit and devouring the spirits of the deceased Eldar trapped within. Its fate after that battle is unknown.

* LifeDrain: In the fluff, the Doom did this to the souls in Malan'tai's Infinity Circuit. In-game, the Doom does this through its Spirit Leech rule.[[labelnote:Explanation]]In every shooting phase, models within 6" of the Doom have to take a Leadership check with 3 dice instead of the normal 2. If they fail, they take wounds equal to the amount over their Leadership they rolled, and the Doom's strength stat increases by that same amount, to a max of 10.[[/labelnote]]
* PutOnABus: The Doom was removed as a playable model in the 6th edition codex, although the Zoanthrope info page in the newest codex has a fluff section talking about it.
* YourSoulIsMine: Invoked in spirit, if not in word, by the Doom's assault on Malan'tai.

!!Deathleaper
%%[[quoteright:150:http://static.tvtropes.org/pmwiki/pub/images/wh40k_deathleaper_3849.jpg]]

A unique Lictor, created as the ultimate assassin and psychological weapon, infamous for its skill at terrorizing important targets and disrupting enemy morale.

* ChameleonCamouflage: And he's so good at it that if you try and shoot him, your Ballistic Skill automatically drops to 1.
* ParanoiaFuel: InUniverse, this is its function.

!!The Parasite of Mortrex
[[quoteright:150:http://static.tvtropes.org/pmwiki/pub/images/mortrex150_5766.jpg]]

A grotesque flying abomination first seen on Mortrex, an Imperial fortress-world in the Ultima Segmentum, the Parasite earned its name and its legendary reputation for its ability to implant Ripper eggs into its victims, causing them to be devoured from the inside out by rapidly-hatching swarms. Within two weeks of its appearance, it had destroyed the entire planet of Mortrex, which was overrun by vast tides of ravenous Ripper Swarms. It has not been seen since, but the Imperial Guard are certain it's out there, somewhere...

* BewareMyStingerTail: Because the barbed ovipositor is for implanting eggs.
* FacefulOfAlienWingWong: Can inject larval Rippers into victims through its tail-stinger.
* MookMaker: Those killed by its Implant attack create new bases of Ripper Swarms.
* PutOnABus: The Parasite was removed as a playable model in the 6th edition codex.

[[/folder]]

[[folder: Zoats]]
[[quoteright:250:http://static.tvtropes.org/pmwiki/pub/images/zoat_40k_6816.jpg]]

A little known and largely forgotten piece of early Tyranid lore, the Zoats were a centaur-like slave race engineered by the Tyranids. In first edition days, nearly half a Tyranid force had to be made out of Zoats. They were never popular, and never made the transition to the next edition, only having a few references to them be dropped in the background of the third edition. Much like the Squats, they are something considered to have been dropped from the franchise.

* ChuckCunninghamSyndrome: Quietly dropped when the second edition was released. Details about their removal went unremarked until a footnote in the third edition explained their fate (see below.)
* ContinuityNod- Though they haven't been brought BackFromTheDead, many fans think that the design of the Tyranid Hive Guard was a bit of a nod to the Zoats.
* [[DroppedABridgeOnHim Dropped A Hive Fleet On Them]]: The revamped lore indicated that the Tyranids created them as a semi-independent group to go ahead of the Hive Fleets as vanguards and disrupt targets for consumption. But being independent, they TurnedAgainstTheirMasters. However, finding themselves trapped between a rock and a Hive Fleet, they were quickly wiped out as the Hive Fleets caught up to them. The few who survived were spotted in Tyranid swarms, but their numbers dwindled as the Hive Fleets evolved to no longer need them.
* EarlyInstallmentWeirdness: They never made it past the first edition, the [[CharacterizationMarchesOn March of Characterization]] from the Tyranids made them incompatible.
* GasMaskMooks: Zoats could only breath in very specific atmospheric conditions, and thus when not in a controlled environment like their ships they would each wear rebreathers.
* MouthOfSauron: The Zoats were to be harbingers of the Hive Fleet, letting others know that they Tyranids were coming for them, encouraging prey planets to surrender to the inevitable. [[CharacterizationMarchesOn This did not last long]].
* OrganicTechnology: They used much of it, though to a less animated extent than the Hive Fleets. For example, their ships were organic, but not {{Living Ship}}s, having their hull grown like a shell, then hollowed out and having more conventional technology built into it. Their ability to freely combine both organic technology and conventional technology allowed the Tyranid forces to employ things like bolters and missile launchers, in addition to their more usual fare.
* OurCentaursAreDifferent: They are lizard-like slaves to a HordeOfAlienLocusts.
* ServantRace: For the Tyranids.
* YouHaveOutlivedYourUsefulness: The justification given for why the Hive Fleets phased them out.
[[/folder]]

----