In the table-top wargame Warhammer 40,000, Tyranids are a swarm of aliens in many sizes and shapes. The most well known type of Tyranid is the horrific Genestealer. At first genestealers were independent monsters/race used in WH40K fiction and most importantly in table-top game Space Hulk. Soon the concept grew to a whole Tyranid race, of which genestealers are only one part.

Tyranids form a superorganism: they travel the universe on their Hive Fleets, destroying all ecologies in their path. They are psychically linked via their Hive Mind, which gives them great abilities to strategize and coordinate. When one Tyranid sees something, within an instant the entire Tyranid race is aware of it.

The mentality behind the Tyranid race can be summed up by the phrase "quantity has a quality all its own". From the lowliest Ripper swarm, to the deadliest Hive Tyrant, the signature trademark of Tyranids is that they swarm over their foes, obliterating everything before them without regard for species or race, seeing all life as merely fresh meat; new gene code to be assimilated, processed, and cycled into the spawning cycle to generate deadlier species off-shoots.

Tyranid Battle Tactics

Tyranids often attempt to first take a planet through deception. Space Hulks and other derelict spacecraft are infested with Genestealers, which quickly familiarize themselves with the layout of their new home, then hibernate.

When the Hulk is eventually discovered, the Genestealers attack the exploration crew, sometimes killing some crewmembers, but always leaving at least one survivor who is implanted with a seed, similar to a Xenomorph Facehugger.

Unlike the facehugger, this infestation is never fatal, but instead subtly alters the victims DNA, giving them a strong urge to mate. The child that results from this union will be a Genestealer hybrid, which now has the complete loyalty of its parents. The Hybrids continue to breed and multiply among the population, eventually forming a Genestealer Cult. As the Cult grows in numbers, it begins to spread its influence throught the planet, placing its members in positions of power within the government and the military. At the same time, it begins to emit a psychic signal through the warp that acts as a beacon for the Hive Fleet.

As the fleet nears the doomed world, the cult 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 Tyanid organisms, which will begin to alter the planet's surface and ecosystem to make it easier to digest.

If the Hive Fleet is victorious, the fleet will descend to the planet, inhaling the atmosphere, drinking the seas, and basically consuming its surface until nothing more than a lifeless ball of rock remains.

On the battlefield, Tyranid tactics are based around the notion of superior numbers. 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 this if they are commanded by a worthy commander.

Tyranid Storyline

In Warhammer 40,000, the Tyranids appeared from the eastern part of the Galaxy, and sent a large fleet of troops (called Hive Fleet Behemoth ) directly at the center of the galaxy. They were defeated, barely, by the efforts of the Ultramarines chapter of Space Marines, although the Ultramarines suffered devastating losses.

Later the Tyranids returned with Hive Fleet Kraken which, instead of throwing one mass of troops against the Imperium, split into countless smaller fleets, each small fleet enveloping whole systems before reinforcements could arrive. The brunt of the this new attack was borne by the Space Marine chapters Scythes of the Emperor and Lamenters; the former chapter was completely destroyed. At the same time, Hive Fleet Leviathan appeared from "below" the Galaxy (in a 3D sense, on the Z axis) and attacked from two points, cutting off large portions of the galaxy from reinforcements.

Tyranid Species

Tyranids appear in a multitude of genera, and all have an extremely rapid rate of evolution, 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 immediate purpose.

• Hive Tyrants are large and enormously strong Tyranids, acting as 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. They are monsters at both close combat and ranged attack, with the ability to excel in both. Sometimes they are spawned with wings. Imperial Techno-Magi believe that Hive Tyrants form the repository of the hive fleet's collective consciousness, which means they completely embody the Hive Mind but their destruction does not in any way diminish its presence.

• 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 defences when they are active in their purpose as bodyguards. On occasion Carnifex also benefit from the Tyrant Guard's protection. Tyrant Guard are scientifically rumoured to contain the DNA of defeated Space Marines chapters, but the Imperium considers this blasphemy and denies its possibility.

• Tyranid Warriors are synaptic foot troops for the swarm. In between the size of a Tyrant and a Gaunt, they serve as psychic resonators and assist in guiding the lesser 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 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.

• Gaunts are the basic staple 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 bio-weapon symbiotes, including the dreaded spike rifle.

• Gargoyles are essentially winged variants of the Gaunt genus. They follow many similar traits, including a smaller size and physical prowess than most Tyranid organisms. Like their cousin, the Gaunt, they are capable of being armed with a large host of symbiotic weaponry.

• Rippers are small, snake-like organisms designed to devour living matter so that new DNA and nutritients can be absorbed by the Hive ships.

• Genestealers are ferocius creatures, supposedly derived from human DNA, that are used as a vanguard to the Tyranid invasions. They infiltrate the 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 – also known as Screamer Killers – are huge, hulking living battering rams, armed with a variety of symbiotic weaponry. Even stronger than the Hive Tyrants, they are used for assaulting fortified positions and tank formations.

• Raveners appear to be related to both Rippers and Tyranid Warriors. These large beasts are designed for fast assults against lighter enemies, and dig through the ground to perform surprise raids.

• Zoanthropes are a type of psychic artillery, whose higly 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 Eldar DNA.

• Biovores are sluggish 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.

• Norn-Queens are believed to be the mysterious female counterparts to the Hive Tyrants. They lead the Tyranid swarms and direct the evolutionary paths to take. They invariably stay aboard their Hive Ships.

• Dominatrixes are the Norn-Queen's link to the ground forces. They are huge monsters, almost as large as a Bio-Titan, symbiotically fused with a smaller (Warrior-sized) entity which acts as a psychic link to the Queen abord her ship.