The Red Emperor does not acknowledge the existence of other peers – his sovereignty and lawful authority is everywhere touched by the light of the Red Moon (ie., the entire Surface World). Near him, in the Heartlands, the world is governed by his satraps – powerful people who collect taxes and organize worship for the Red Emperor, and are tasked with maintaining the peace. Further beyond are the Provinces – ruled by barbarians who have submitted to their rightful ruler. Beyond that are the allies – barbarians who follow the direction of the Red Emperor but have not submitted to him. Beyond that are only rebels – some are rich and powerful, others savage and benighted. This is model is obviously derived from the Solar Empire system. The Red Emperor is perfectly willing to pay barbarians and rebels to submit to him or at least to be allies. What is important is that they acknowledge his position as the sole pillar of legitimacy in the world.
All universal empires are Yelm’s empire. At least on some level.
The Lunar Empire does not acknowledge any peers. Now that does not mean it feels compelled to conquer the world – and in fact it is even willing to accept only a tacit acknowledgement of the Red Emperor’s suzerainty. Which plenty of folk do – the Eolians, the Talatastarings, the Char’un, Garsting, etc. But not the Prince of Sartar, the Holy Country, or most of the tribes of Prax and Pent.
Isn’t this the attitude of the Brithini and possibly the Seshnegi/Rokari?
Not really. The Brithini never claimed to be universal rulers. They claim to possess universal truths, but believe that most of the beings of the cosmos are too deluded, foolish, arrogant, etc., to see those truths.The same thing holds true with the various Malkioni groups. None assert claims of universal legitimacy. Even the Middle Sea Empire made its claims based on Power and superior Knowledge, not that it had an inherent authority. They sought to rule the world because they could – that’s a subtle but important difference.
In the end, Yelm and Orlanth did acknowledge each other and reconcile, right? both religions hold that their respective gods made amends and also that in Time their worshipers made trouble. So Yelm is always making the compromise with Orlanth, but also is always the arrogant and foolish emperor, and always in the Weapons Contests with Orlanth. All of these are always true, simultaneously. Worshipers in Time of course can pick whichever always they want at the moment.