Leviathan announced itself not with a single battle but with the slow, dawning horror of cartographers realizing that an entire quadrant's worth of stars were going dark in sequence. It arrived from the galactic south in numbers that dwarfed its predecessors, splitting into arms that threatened core Imperial holdings even as other splinters ranged far beyond, testing the defenses of alien empires who had never before faced such a foe.
What distinguished Leviathan was the sophistication of its bio-forms, monstrous creatures adapted specifically to break fortress worlds, crack starship hulls, and shrug off weapons that had proven devastating against earlier fleets. Its vanguard organisms seemed to anticipate Imperial countermeasures before they were even deployed, a chilling suggestion that the Hive Mind had been studying humanity's tactics since Behemoth's first incursion generations earlier.
The fighting against Leviathan stretched for years without a clean resolution, forcing alliances of convenience between factions who would otherwise never stand shoulder to shoulder. Its passage left behind dead systems, broken fleets, and a lingering unease among survivors that they had faced not a single fleet but a rehearsal for something larger still to come.
Tyranids
Order of battle
The Hive Fleet Leviathan field the units of the Tyranids — a detachment from the roster:
Kindred formations
Other Tyranids formations
Hive Fleet BehemothThe first hive fleet to breach Imperial space, a brutal vanguard that taught humanity the true meaning of extinction.
Hive Fleet GorgonAn endlessly adaptive tendril whose bio-forms rewrite their own flesh mid-campaign, answering any weapon turned against them within a single generation.
Hive Fleet HydraA numberless deluge that trails in Leviathan's wake, devouring the broken splinters of older fleets and drowning every prey world beneath an unstoppable tide of bodies.
Hive Fleet JormungandrA subterranean hive fleet that honeycombs whole worlds with tunnels and armours its bio-ships in asteroid rock, collapsing cities from below before the defenders know war has come.
Hive Fleet KrakenA fractured, unpredictable tide that scattered across a thousand worlds at once, proving no single line of defense could contain it.
Hive Fleet KronosThe Hive Mind's answer to Chaos, a fleet of suffocating psychic silence and merciless ranged bombardment that withers daemons and seals the wounds of the warp.