Board Thread:Warhammer 40k General Discussion/@comment-14745711-20130906234048/@comment-6078851-20141111152950

the problem with the imperium allying though is their rampant xenophobia. even if humanity started to rise again after the final death of emps they would still see themselves (the majority of the race at least) as superior to other races. as you said humanity were colonizing the galaxy before emps stepped into the limelight, but they were also rampantly xenophobic with an over inflated sense of their own importance long, long before emps made himself known, and after emps' death i don't see that attitude changing any time soon, making any lasting and trusting alliances highly unlikely.

but tyranids will almost never see each other as strangers. hive fleets have been known to fight each other, but these fights are the will of the hive mind to allow different bio-mass genes to be spread further throughout other hive fleets, allowing for a greater diversity of bioforms, as well as the winning hive fleet becoming stronger. the only way tyranids would see each other as strangers (not counting bioforms out of range of a synapse bioform) is if the hive mind was actually destroyed, and given that the hive mind is the amalgamation of every single tyranid bioform in existence the only way to destroy the hive mind would be to destroy the tyranid race.