This empire is still going on and continuing to acquire more planets, so this article will likely become outdated.
Also, technically, they have not conquered any empires, they just acquired planets that were not already part of an empire. If a nation joined them, it was willingly.
This empire started out as many tribes spread out over many moons and planets, these planets orbited stars that orbited ultra-stars. These ultra-stars orbited one massive hyper-star. Once one of the groups developed space travel, they flew to the nearest moon, which was also populated. Over many centuries, they fought, but eventually united. They started to build a nation over all the planets and moons and eventually had the technology to expand.
Intelligent, cultured and democratic, they wish to give their knowledge to other civilizations, discretely, or so we think, (you won't even know if they gave their knowledge).
NOTE: At this point I would just like to say that I will neither confirm nor deny the rumors that the Hyperstarian Empire has had any interaction with Earth.
Species Appearance, Ideology, and Flag
There are many species in this empire including humans that were brought from Earth, their descendants, and anthropomorphic animals, but the main species is reptilian, winged. 9ft/3m, lifespan of 200 - 300 years.
They have a democracy, where they vote for their leaders every 20 years.
(a little long for an Earth democracy, but voting itself takes 1 year)
Their flag is a red and green banner with many, unpatterned stars on it.