

Despite these setbacks, the Tyranids continued to advance into the Galaxy through a variety of smaller Hive Fleets. After Behemoth, the next major Hive Fleet to move into the Galaxy was Kraken in 992.M41, though tendrils of this Hive Fleet were defeated by the Imperium Ichar IV Campaign and by the Eldar at the Battle of Iyanden. However this was hardly the end of the Tyranid menace. Hive Fleet Behemoth was largely defeated at the Battle of Macragge in 745. This discovery raised the disquieting possibility that other dormant Hive units are already "salted" around the Imperium as a whole, waiting for a new Hive Fleet to awaken them.

M41, a Bio-ship was discovered beneath the surface of Nusquam Fundumentibus, where it had lain dormant since around M34. Records kept by the Ordo Xenos of the Inquisition suggest contact with Tyranid bio-forms as early back as M35 even more remarkable, in 937. Some of the Galaxy's most notorious predatory beasts, such as the Catachan Devil or the Fenrisian Kraken, are guessed to be the descendants of ancient Hive Fleets. However, reexamination of Imperial records has led to speculation that the Tyranids have been invading, or at least probing, the Galaxy for much longer.

M41, when the Hive Fleet later known as Behemoth invaded the Eastern Fringe and annihilated planet Tyran. The Imperium's first official contact with the Tyranid race was in 741. According to another source, they have consumed one thousand galaxies and are responsible for the annihilation of millions of intelligent species. It is possible that they have been preying on other galaxies since time immemorial. Indeed their very name is but a title given to them by the Imperium, named after the planet where they were first encountered ( Tyran). The Tyranids were first attracted to the Milky Way Galaxy when the xenos communication device known as the Pharos was overloaded in the Battle of Sotha during the Horus Heresy. It is unknown which galaxy they originated from, or for how long the Tyranid race has been on its genocidal rampage, but it is believed that it is the Astronomican that is drawing the Tyranid Hive Fleet to threaten the galaxy. The exact origin of the Tyranids themselves is unclear, save the fact that they are not of The Galaxy and have only recently arrived here after traveling countless millennia in the intergalactic void.
