"The armour of a Land Raider, the strength of a Thunderfire Cannon, the accuracy of a veteran Devastator, and the discipline of the Emperor's Finest -- this is the Tyranid Hive Guard."
- — Aloysius at the Battle of Macragge, 745.M41
The Hive Guard are a strange Tyranid life form. They are usually not seen until the capillary towers and spore chimneys have formed on the surface of a world in the later stages of a Tyranid invasion. Such structures are vital to the Tyranids' attempt to consume a world, and the Hive Mind has created a specific beast for their protection -- the Hive Guard.
The Hive Guard stands out as a unique creature even amongst the Tyranids in its extreme specialization for its role. The Hive Guard's six-legged form provides it with a stable-firing platform for its deadly Impaler Cannon.
Hive Guard play a crucial role in the final stages of a Tyranid invasion, when all of the planetary bio-mass the xenos have harvested and partially digested must be transported to the Hive Ships. In these last stages, enormous capillary towers and spore chimneys emerge from the ground, the former growing with astounding speed past the upper reaches of the planet’s atmosphere, to channel the processed organic soup to orbiting Hive Ships.
As these towers and chimneys enable the Tyranids to achieve the ultimate goal of their planetary invasions, the Tyranids take particular care to defend these structures well. Indeed, the Hive Mind seems to have developed the Hive Guard specifically to fulfil the important function of standing watch over these towers. Typical of the ever-efficient Tyranids, Hive Guard have a very short incubation period and are spawned only when needed in the final stages of the harvest and only when the capillary towers and spore chimneys face an enemy threat.
Xenobiologists have determined that Hive Guard have some capacity for telepathy, though not to the extent of the more sophisticated synapse creatures like Hive Tyrants. This low-level psychic capacity enables the creatures both to see through the eyes of their fellow xenos in order to target enemies with their Impaler Cannons and to communicate with the shard-beasts that are fused to the Cannon’s projectiles, long bony spikes up to 2 metres in length.
Through the psychic link that Hive Guard and shard-beast share, the Hive Guard can direct the symbiotic organisms to alter the course of the projectiles in mid trajectory, by moving membranous fins to act as wing flaps or rudders that steer the missiles. As such, Hive Guard need not make direct visual contact with enemy targets to fire upon them. Field reports from Imperial troops indicate that the Hive Guard can target unseen foes with uncanny accuracy even over moderate distances.
Unlike most Tyranid creatures, which advance upon any non-Tyranid life forms with seemingly reckless abandon, Hive Guard instinctively function as sentries who seldom charge or pursue their foes. The Hive Guard’s task is to stand sentinel over the capillary towers, and only in moments of desperation will the Hive Mind prompt these stalwart guardians to advance upon the enemy.
- Impaler Cannon - The living shard beasts of the Hive Guard's Impaler Cannon are little creatures that guide the large harpoon like spikes. These bony missiles are twice the height of a man and can be fired indirectly at targets in cover. It can even be used against transports and other lightly armoured vehicles in a pinch.
- Codex: Tyranids (6th Edition) (Digital Edition), pp. 109-110
- Deathwatch: The Jericho Reach (RPG), pg. 179