The Hive Mind is the gestalt collective consciousness of the entire Tyranid race, a psychic embodiment of the Tyranid instincts and racial imperatives to devour and destroy.
It is not a single mind capable of small, conscious thought the way a Human's mind works, but instead it is a grand agglomeration created from the psychic presence of untold billions of Tyranid creatures. It is a nightmarish and unfathomable intelligence that allows Tyranids to coordinate and adapt as if every Tyranid creature is merely a part of a single massive organism, one which is utterly focused on consuming all other life.
Shadow in the Warp
The psychic presence of the Hive Mind is so powerful that it radiates out of Tyranids like a flood. This permeating psychic power on the gigantic scale of a Hive Fleet distorts the Warp for light years around the fleet's position, preventing Imperial Astropaths from sending or receiving telepathic messages, stopping spacecraft entering the warp[Needs Citation] and forcing spacecraft already in the warp wildly off-course as warp travel becomes increasingly unpredictable. This invasive "shadow in the warp" sows terror and confusion on prey worlds as it traps and prevents the doomed inhabitants from calling for assistance. It even penetrates into the minds of nearby creatures and manifests as a primal malaise that can never be expelled. If a creature has psychic potential, the horror they feel is magnified tenfold and using their psychic abilities could drive them into incurable insanity. As a Hive Fleet approaches a target planet, whole populations will plunge into madness and despair even before the first Tyranids have made planetfall.
Almost every attempt by a psyker to make contact with the Hive Mind results in insanity or death, either because it would require an incredibly powerful psyker to withstand the Hive Mind's awesome psychic presence or because the nature of the Hive Mind is completely beyond the comprehension of human beings. This however can be argued, as Chief Librarian Tigurius of the Ultramarines seems to have some form of relationship with the Hive Mind, as he is able to make remarkable predictions about the Tyranids and their movements. This could be due to his uncanny gift of making predictions in general, but the accuracy and frequency of his predictions about the great devourer seem to show he has indeed tapped into the Hive Mind, a feat thought possible only by a psyker of the Emperor's degree.[Needs Citation]
On the battlefield, certain large and relatively autonomous Tyranid creatures, such as the Hive Tyrant or the Tyranid Warrior, are able to telepathically exert the Hive Mind's influence in order to control smaller Tyranid creatures, which without the Hive Mind would revert to genetically instinctive behavior of feeding and self-preservation. These Synapse Creatures focus the Hive Mind into nodal points that quell the natural instincts of nearby small Tyranid creatures and are essential for the swarm to operate effectively.
A smaller and more localised version of the Hive Mind is created by the interlinking telepathy of a Genestealer Brood. This Brood Mind is used to control host victims impregnated with Genestealer genetic material. It also fulfills the Genestealer's role as infiltrators as the Brood Mind acts as a psychic beacon to draw a Hive Fleet towards the planet it is centered on. Then when the Hive Fleet comes within a few hundred light years of the infected world, a subliminal reaction is triggered in the Brood Mind to goad the Genestealers into a frenzy of killing and breeding. Thus collapsing the society in which they were hiding and making way for the Tyranid invasion.
The concept of a Hive Mind is so utterly alien and terrifying to a human mind that the Imperium searches vainly for the higher beings they suppose control the hive fleets, and though such mighty creatures exist they no more control the hive mind than single brain cells control a man's body. It is the sum of the hive mind which motivates it, not its constituent parts.[Needs Citation]
Some Technomagi of the Adeptus Mechanicus think that the Hive Mind might just be the psychic network that links the Tyranid race and permits them to access the collective knowledge of the location and disposition of all other Tyranid creatures. Others think that it is in fact an incredibly powerful psychic monster using the Tyranids as puppets, while others think that it might be one of the Old Ones.[Needs Citation]
- 1: Codex: Tyranids (5th Edition), pgs. 6-7
- 2: Space Hulk Mission Book (3rd Edition), pgs. 46-47
- 3: Battlefleet Gothic Armada, pg. 80
- Codex: Tyranids (4th Edition), [Needs Citation]
- White Dwarf #145 (1992), Tyranid army list
- Codex: Space Marines (5th Edition), [Needs Citation]