A recent tendril of the Tyranid invasion, Hive Fleet Hydra drifts along in the wake of Hive Fleet Leviathan, seeking out defeated splinters of previous Hive Fleets in order to cannibalise them and absorb their genetic memory. The Hydra is a relatively minor Hive Fleet that some Imperial reports indicate was first detected entering the galaxy at its eastern extremes or from the galactic south; the discrepancy has not been resolved. Hive Fleet Hydra was prematurely awakened from its hibernation as it drifted through the intergalactic void towards the Milky Way Galaxy by Drukhari pirates who boarded several of the fleet's largest bio-ships in hopes of obtaining rare genetic specimens for the fleshcrafters of Commorragh.
While the Hydra appears to be relatively small in size compared to the larger Hive Fleets that fought the Tyrannic Wars, this impression is deceiving; it is still capable of unleashing vast hordes of bioforms, burying its prey under sheer weight of numbers.
When approaching a prey world, Hydra seeds its atmosphere with thousands upon thousands of spore clusters, each containing scores of dormant Hormagaunts and Termagants. When its initial invasion swarms encounter resistance, each slain organism releases a powerful synaptic pulse. Upon sensing this psychic death cry, the embedded spore clusters immediately release their living cargo. Instinctively these reinforcements converge upon the kill-signal, driven to a frenzy by the echo in their predatory consciousness. Thus, a single pack of slaughtered Gaunts swiftly becomes a cluster of swarming xenos bodies, which soon becomes a living tidal wave of chitin and flesh.
On several occasions Hive Fleet Hydra has swept into sectors of space that have only recently repelled a Tyranid assault, falling upon and consuming both weary survivors and the carcasses of fire-gutted bio-ships, before disappearing into the void once again. Whether Hydra's unnerving generative capacity is related to this pattern of feeding upon members of its own race is a subject of heated debate amongst Imperial scientists. Many experts, most notably the famed Magos Xenobiologis Echros Van-Zendrech, have theorised that this development may signal the next stage in the Tyranid invasion -- an autophagic cycle that will unleash a new, more resilient wave of Tyranid bioforms upon the fractured galaxy.
Hive Fleet History
There are seemingly no limits to the swarms that Hive Fleet Hydra can bring to bear against its prey. To do battle with this nightmare is to drown beneath a tide of surging xenos bodies.
- The Hydra Stirs (Unknown Date.M41) - Drukhari of the Poisoned Fang Kabal encounter the still-dormant Hive Fleet Hydra. Instead of destroying it, the Kabalites board the largest bio-vessels, intent on bringing specimens back to the Haemonculi. However, they are unprepared for the rate at which the bio-ships awaken. Every Dark Eldar pirate that sets foot inside one of the vessels is killed, butchered by a tide of rapidly spawned Tyranids. Those Drukhari still aboard their vessels attempt to escape, but for every drone ship they destroy two more take its place. Prematurely awakened from its slumber, Hive Fleet Hydra accelerates its advance into the galaxy to slake its hunger.
- A Grim Analysis (Unknown Date.M41) - Magos Xenobiologis Echros Van-Zendrech leads several survey ships to the Locis System, where Hive Fleet Hydra is in the final stages of devouring the Mining World of Korstock. Van-Zendrech watches the consumption of the civilian population with keen interest, noting Hive Fleet Hydra's unique attack patterns.
- The Hunters Hunted (Unknown Date.M41) - A strike force of White Scars hunts the Hydra across the sand dunes of Haadekh. Veterans of countless xenos wars, the Space Marines know that the best method of fighting Tyranids is to cut the head from the beast, sending the swarm into confusion. However, each synapse creature the White Scars slay sends out a psychic scream, attracting fresh swarms of Tyranids to their location. Soon they are surrounded. Warriors to the end, the White Scars sell their lives dearly. Their sacrifice draws Hydra's swarms away from Haadekh's equatorial cities, giving the Imperium time to evacuate key personnel.
- Triumph To Disaster (Unknown Date.M41) - After solar months of campaigning, the armies of Lord General Syvar Daeus turn back a tendril of Hive Fleet Leviathan from the borders of the Corilanus System. In his honour a great Imperial Triumph is held on the planet of Ollfyre. Just as Daeus' legions reach the Plaza of Fallen Heroes, shadows begin to fall across the millions of onlookers. Looking up, the terrified populace sees its doom approaching -- countless spores darken the skies, and beyond that vast, organic shapes drift into orbit, blocking the light from Corilanus' binary suns. The Hydra has come, drawn by the death throes of its defeated kin.
- Codex: Tyranids (8th Edition), pg. 35
- Codex: Tyranids (6th Edition), pg. 31
- Codex: Tyranids (5th Edition), pg. 38
- Warhammer 40,000: Rulebook (8th Edition), pg. 166
- Warhammer 40,000: Rulebook (5th Edition), pg. 137