No, "Xenomorph" is a blanket term to describe all aliens, mostly used by people who hate them and became popular when the Dark Days/Great War broke out. There are an unimaginable amount of civilizations in my universe and the humans barely have any contact with them save for the ones that are local to their sector of the universe. Sorry for the confusion! But then these people have to rebuild during a huge war where most of the land is completely uninhabitable and must flee to land that is habitable and that land is incredibly small. Resources allocation and the lack of available resources to mine around them would make it impossible for people to go back to rebuilding civilization as it was before. Not to mention, it's been possibly decades since the war happened and by then, several generations of children have been born who do not know the world before the war happened. In my world, quintillions of people are crammed into a very small space and are pretty much cornered by Xenomorphs and the demon legions. Crime goes through the roof, riots/protests everywhere, starving people resort to cannibalism out of desperation while everybody alive doesn't even know about the past. Professions are different, cultures are different, ambition or desires are different and there is a totalitarian regime that controls everybody and what they do. If the royal family does not want civilization to rebuild, all they need to do is to simply not reveal any knowledge or technology and intentionally keep them in the dark ages. Since they were immortal and powerful, they lived for many thousands of years. That's exactly why it would be impossible to rebuild, there isn't anyone alive that knows anything about the old world or has any knowledge of the old world. Not only that but innovation and creativity would not only get you in trouble with the authorities but also be really difficult with strained resources, criminal gangs/cartels, a huge war that has galaxies disappearing, demon legions that swarm and eat everything and no available libraries for information to educate themselves. What technology the royal family chooses to give to the civilization is what they'll receive. The Wreath is a weaponized gamma ray burst, it's the only thing left from the old world they have and that's because the royal family gave it to them. They've reverse engineered a lot of that technology to produce some technology but nothing they created was ever as powerful as what they had in the Enlightenment Era. Think soviet technology mixed with reverse engineered future technology, they have powerful technology but the actual technology they reverse engineer they have no clue how to use or what the purpose was so they just use it for their own purposes that make it far weaker. So for example, a Dyson Ring would've just been used to create a very limited power source of a warship than it's original purpose to produce tons of energy for a civilization. A Wreath used to be able to destroy huge sectors of space but it's limited to just a star system or a galaxy now.