The Flying Fleet (1929) - IMDb
For intelligent races such as the humans of the  Imperium of Man , whose means of interstellar communication and travel rely upon highly specialised psykers such as Astropaths and Navigators , the Shadow in the Warp is one of the deadliest facets of

For intelligent races such as the humans of the  Imperium of Man , whose means of interstellar communication and travel rely upon highly specialised psykers such as Astropaths and Navigators , the Shadow in the Warp is one of the deadliest facets of the Tyranid menace. Bereft of their means to call for reinforcements or safely navigate the surrounding space, the worlds of the Imperium are easily isolated from the wider galaxy. This means that, by the time the Shadow in the Warp falls, it is already too late; these beleaguered planets are effectively on their own. They must fend for themselves and face the Tyranid swarm with the weapons they have at hand, or die in the attempt.

There are many other Hive Fleets known to exist in the galaxy or to be approaching it from the vast void of intergalactic space. Several of these Hive Fleets are splinter fleets of the original three to invade the galaxy and include:

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