The consumption phase of an invasion, strictly speaking, begins when the first mycetic spores are leeched into the atmosphere to prepare it for eventual biological assimilation, but this process begins proper once the last major resistance is neutralized.

The surface of a world undergoing the final stages of Tyranid assault is truly a vision from a nightmare. Feeder organisms pupated in the carcasses of native life forms burst forth and ravage the landscape of every last trace of biological matter. These creatures have no true digestive system of their own. Instead, they exist only to swallow whole everything they encounter before throwing themselves bodily into vast lakes of gastric fluids known as digestion pools, where their biological mass and that of everything they have ingested are rendered down into a thick, nutrient-rich gruel that will be harvested by the hive ships in orbit.

As the Tyranid digestion pools swell, the hive ships cluster in low orbit. Vast capillary towers emerge from the pools and push impossibly high into the atmosphere. The towers link up with the writhing, sucking proboscis-like feeding tubes of the hive ships and pulse with sickening peristaltic action as the rendered biomass is pumped upward and distributed to the greedy clusters of bio-vessels.

At this stage, the biomass of any infested organisms cultivated on the world is added to the harvest. The minds of these creatures are by this point entirely controlled by the hive fleet’s gestalt will, and they march blank-faced into the depths of the digestion pools to be rendered down into nutrients.

Within days, the rampant mutation of the native plant life is ended, its mass consumed by Rippers or broken down by bacterial agents to add to the digestion pools. By this stage, the processes initiated by the actions of the mutant flora have utterly changed the atmosphere and produced an oxygen-rich environment in which further harvesting is accelerated, until all biological matter is broken down and transferred to the suckling hive ships.

The final stage is the harvesting of the world’s atmosphere and seas, when the hive fleet’s drone-ship haulers descend to low orbit and gorge themselves on every last useful element for later use as fuel for the hive fleet’s journey to the next prey world and the creation of yet more warrior organisms. The hive fleet then departs, leaving behind it a desolate rock, stripped of every last vestige of life, right down to the molecular level. The hive fleet will resume its endless conquest. Its only imperative to feed, survive, and multiply until the galaxy is a dry, withered husk, whereupon it will leave once more, setting its unknowable desires on the next feeding ground, untold billions of light years distant.

As the Tyranid hive fleets consume a planet, digestion pools are created to break down all living matter. Everything that is ingested in the pool is turned into a thick primordial soup that is harvested by the hive fleets. In this final stage of invasion, the planet’s elements are stripped away, and the hive fleets then move on to the next prey world.

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