Where the Tyranid Hive Fleet Kronos travels, the Shadow in the Warp is at its most suffocatingly powerful. So strong is the psychic connection between Kronos and the Hive Mind, that a stifling aura of null power drifts ahead of its invasion swarms, agonising psychically active foes and draining their spiritual energy to bolster its own hosts. Even as this phenomena throws the enemy into fearful confusion, thousands upon thousands of warrior-forms advance, unleashing a storm of organic missiles; Kronos avoids engaging its prey at close range when possible, for the prey it hunts revels in brutal close-quarters fighting, and thus a ranged kill is a more efficient method of extermination.
The raw matter of Chaos is anathema to the Tyranids, for it is inconstant and ethereal, possessing none of the nourishment that the Hive Fleets require to sate their endless hunger. Thus, the Tyranids -- when possible -- avoid areas plagued by Warp Storms and daemonic activity. As the impure essence of the Immaterium pours into realspace across the galaxy in the wake of the Great Rift's birth, this is becoming increasingly difficult. Vital resources are being denied to the hive fleets as entire sectors are consumed by Chaos, and the Hive Mind has been forced to react to a looming catastrophe.
Hive Fleet Kronos appears to be the Hive Mind's first solution. This new terror is tracing a coreward path along the line of the Great Rift. Tendrils of Hive Fleet Leviathan have diverted from their original course, leaving behind defenceless worlds for Kronos to consume. It uses such offerings well. The nascent Hive Fleet appears to be zeroing in on areas of intense psychic activity that threaten to tear the breach between realities wider. Scores of planets conquered by Chaos-worshipping cultists and Warp-spawned abominations have fallen in its path, and Kronos has obliterated them all, like a maggot eating the corruption from an infected wound.
Psykers, Chaos worshippers and creatures of the Warp are the favoured quarry of Hive Fleet Kronos. The organisms spawned by its bio-ships are perfectly designed to eradicate the taint of the Immaterium.
- Battle of The Wolf's Head (Unknown Date.M42) - An Imperial fleet under the command of Admiral Groesson is engaging a massive Chaos Warfleet at the Wolf's Head Nebula when scores of bio-vessels enter the battle. Ignoring the Imperial ships, the Tyranids smash their way into the Chaos formation, swarming over the colossal Despoiler-class Battleship at its centre. Not questioning his good fortune, Groesson unleashes a final salvo and orders the retreat.
- Second Battle of Shadowbrink (Unknown Date.M42) - The world of Shadowbrink, where Hive Fleet Leviathan once defeated a vast daemonic force, erupts with Chaos energy as the Great Rift spreads its influence, and daemons once again walk upon its surface. Drawn by Shadowbrink's malevolent aura, Hive Fleet Kronos arrives in orbit above the world. The Hive Mind deposits spores and swarms of organisms at eight points across the planet's surface, areas of heightened Warp activity that are growing stronger with every passing moment. A neural node of Maleceptors and Zoanthropes leads each Tyranid host, and around these psychic organisms the Shadow in the Warp reaches such intensity that the wounds in reality begin to close. Khorne's daemonic legions storm towards the Tyranids, but Hive Fleet Kronos refuses to answer the charge. Instead, the daemons are met with a storm of Fleshborer fire, and Tyranid artillery beasts blast apart thousands of Warp-spawned horrors. Slowly but inevitably, the daemons upon Shadowbrink are banished to the Warp.
- Spoiled Feast (Unknown Date.M42) - Hive Fleet Kronos pauses its inexorable momentum to devour a chain of pre-digested worlds left behind by Hive Fleet Leviathan. The rancid gruel that remains has rotted and spoiled, but the capillary towers and ridged proboscises of Kronos' bio-ships devour it all the same.
- Cutting The Signal (Unknown Date.M42) - A tendril of Hive Fleet Kronos converges upon an intense astropathic beacon that a hunting pack of Night Lords have been using to bait lost voidships. The Heretic Astartes scatter and launch harrying attacks against the Tyranids, hoping to redirect the larger Hive Fleet. In turn, Kronos disperses its bio-vessels, laying traps of its own. Unable to lure the Tyranids away from the tortured Astropaths that are broadcasting their siren signal, the Night Lords are forced to retreat.
- Codex: Tyranids (8th Edition), pg. 37