Fiat Lux

The story's second half, with the alien invasion required an explanation of why aliens powerful enough to invade 5 worlds simultaneously would not simply blast all five worlds to ruins and move in and rebuild over their shattered corpses. The answer to this question lies in that often-ignored bit of sci-fi, budget problems. The aliens are more than capable of launching a  war of that magnitude, if they desired to do so. A previous Grand Emperor to Syian III fucked up their economy enough, and Syian III moves too slowly to fix it, that the aliens must resort to "merely" occupying these worlds. The alien generals, Ravcel Kerigstophros and Yohanin Kerigstandgros, have to command a massive war with an army in worse shape than the Soviet army of the 1980s.

The alien army is quite large by human standards, and the average buck private of the alien forces can manhandle a US Army Brigade, but the humans and their superhero allies bathe the aliens to such a degree of blood that they pull back. Another world, orbiting 61 Cygni, does the same, but the end result is the aliens recuperate and return with overwhelming force to the degree that Earth and its metahumans, metachimps, and so forth, is conquered. In the process, one of the superheroes is captured, and begins to work on a certain alien...

preparing the way for a false sense of security to be cruelly betrayed the way the Bolsheviks did the Russian Empire of the Tsars.

Interestingly enough, one of the ironic moments comes when the aliens blitzkrieg in the second round through armed gangs of far-right prisoners at a maximum-security prison in the process of occupying the Pacific Northwest, and get into a discussion of barbarism with the Neo-Nazis. The aliens point out that Hitler required three years to murder 20 million, but that their commander required only one and sufficient anger at a rebellion on the outer edges of the former Great Void to slaughter 500 million in just the first year of retaliation alone, and to reduce a society at Class-2 levels to Oldowan-level technology. The Neo-Nazis balk, and then surrender.

Basically, the alien "bad guys" are simply closing in a place as effectively as Russia did to Central Asia, and have a rather Ghenghis-Khan/Timur-esque manner of settling wars. Either surrender quickly, or get reduced to the very beginnings of the Stone Age. Screw Neanderthal level-technology, these bastards turn societies at the level of the Borg and the Federation into barely-at-Erectus level technology...and then colonize the planet, to boot. Needless to say, revolts against them aren't exactly common, but their horrific manners of subjugation have produced seething masses that look to one of the generals and the heir apparent to the Grand Emperor (who is a hybrid and of a different House) as their champion.

Needless to say...they find that social revolution and the rise of a new Empire does not necessarily mean the new Empire is better than the Underlanic Empire. You might say they exchanged the Qing Dynasty for the Maoists or the Tsars for the Stalinists. With no intereggeni between them.