The Tyranids are an extragalactic alien race, whose sole purpose is the consumption of all forms of genetic and biological material in order to evolve and reproduce. Tyranid technology is based entirely on biological engineering. Every function is carried out by living, engineered creatures, each of which collectively forms the Hive Fleet, directed by a single Hive Mind.
The Imperium's first contact with the Tyranids occurred on the Explorator Base Tyran, in the Eastern Fringe, from which the Tyranids are named. Researchers on Tyran had logged reports of worlds being destroyed for many years until an Inquisitor known as Kryptman began to notice a pattern. In 745.M41, Kryptman took a ship to Tyran, but received a report from the world mid-transit; Tyran had been destroyed by the alien menace it had watched for so long. Kryptman arrived on the now-barren planet, determined to learn the truth. After searching, he managed to uncover a data codex buried 3,000 meters below the surface in a borehole by the Planetary Governor.
- Main article: Species of Tyranids
The Tyranid forces are constantly changing and evolving at an unnatural speed. It is unlikely that all types of Tyranids have been seen by the Imperium, and still less unlikely that they will ever all be seen. The most frequently seen species are:
- Hive Tyrants
- Tyrant Guard
- Tyranid Warriors
In addition to these, there are also Dominatrixes which ensure good communication between all of the Tyranid forces. There are also Norn-Queens who live within the Hive Fleet and spawn new Tyranids. Originally creatures called Zoats were part of the Tyranid force and some Magos Biologis believe that they are left over from a much earlier Tyranid invasion, although they appear to have disappeared from common sight.
The Swarm ConsciousnessEdit
See main article: Swarm Consciousness
Within the Tyranid swarm there is no idea of individualism as each unit is linked to the next in a form of swarm consciousness. There is only one reason for the creation of any of the forces involved in Tyranid armies; to implement the will of the swarm consciousness, be it a Hive Tyrant or Ripper Swarm. The consciousness is controlled by the Hive Mind.
See main article: Synapse Creatures
Certain Tyranid units are considered Synapse Creatures, whose job it is to control the lesser species within the swarm. They are capable of receiving and sending orders which they received from the Hive Mind and this connection is vital to the effective running of the Tyranid race for, without it, the swarm would collapse into disarray. Usually they are fielded in relatively large numbers to allow a rapid advance of the lesser creatures to remain in range of a synapse creature.
Tyranid forces are broken up into huge Hive Fleets which appear to be moving independently of each other.
Generally, contact with the Tyranids occurs when a Hive Fleet invades a system for the purpose of harvesting its bio-mass. A Hive Fleet contains an enormous number of Tyranids, and they are brought to bear against resistance in the most efficient manner possible. Below is a general outline of a typical Tyranid planetary assault (in particular, this data is collected from the Tyranid invasion of Dalki-Prime):
- Day 00: Initial mycetic spores are dropped, generally containing Lictors or Genestealers. Infiltration force led by a synapse creature of some kind; reproduction of Tyranid creatures likely begins immediately.
- Day 09: By day 9, Tyranids will have expanded to around 200 km from the drop point, and will likely present a significant threat to PDF troopers and resident Imperial Guard.
- Day 13: Tyranids will have expanded to 700 km from the drop point; may begin infesting local water sources.
- Day 37: Tyranids control area within 2000 km radius of the drop point; basolithic infestation to 5000 km radius.
- Day 48: Tyranid population growth skyrockets, with population doubling approximately every 2.5 days.
- Day 50: Main Hive Fleet arrives, craft generally numbering around 1.5 billion. Psychic contact with planet is cut off by the shadow of the Hive Mind. Any attempts to escape are quickly stopped by the Hive Fleet.
- Day 51: Primary consumption of bio-mass begins (resistance has generally been eliminated by day 51). Brood ships land, releasing Ripper swarms, which consume organic material and depositing them at the reclamation pools. Capillary towers (and the Brood ships) send the material into orbit. Any remaining surface life is eliminated by Gaunts.
- Day 80: Ripper swarms board the Brood ships and return to the Hive Fleet. The hive ships descend into the upper atmosphere and begin collecting it. Reduction in atmospheric pressure causes oceans to boil away, which are also collected. Lack of oceans causes plate tectonic shifts, dramatically increasing volcanic activity. Upon completion, the Hive Fleet re-enters the Warp, in search of fresh prey.
- Day 100: Imperial navy arrives in response to the distress call to find the world lifeless.