Originally Posted by
DDM
That's understating it. Every aspect of their culture, from goverment to social norms, is based upon their religion. And at the core of that is the marriage of their two prime deities Sharra and K'ythri. The mythology was that they were gods at war but their conflict destroyed the galaxy and were forced to marry, creating a new stronger Shi'ar world and finding love in the process. This is why the Shi'ar Empire expands the way it does, they view themselves as not simply conquering other worlds but marrying them through war, integrating their cultures and growing stronger. Representatives from these worlds are then included in the Shi'ar High Council on Chandilar and also put forth their strongest warriors to join the Imperial Guard.
There are downsides to these close theological ties too though. The cultural emphasis on marriage through war has made subjects like art and homesexuality extremely taboo within the Imperium. Lilandra was seen by traditionalists as weak due to her prioritizing peace over conquest and expansion.
Also the M'Krann Crystal is tied into the Shi'ar origin myth as it was a gift from K'ythri to Sharra for their wedding. For the Shi'ar it's also the resting place for the dead and the home of the Phoenix, which they also have a complicated history with.