The number of Beyonders within the Eternal Empire wasn't many, and every single one represented the foundation of not only the Empire but also the species. And in terms of powerful Beyonders, not just those who just entered the Beyonder Realm or were already very powerful, there was even less of them.
For the Eternal Imperium of the Asurya, Grandmaster Byrmellir was one of the pillars of the Empire, together with a few other old fossils of the Asuryani and Votans, who represented the pinnacle of the Imperial power.
Just their presence alone was enough for the other High-Level Civilizations to stay away from declaring all-out war on the Eternal Empire. If the Beyonders started fighting among each other, especially the ones with Super-High Risk Primal Psyker Ability or other powerful abilities, then it would be an unprecedented degree of destruction.
