An alien empire in the Champions Universe.
Founded approximately 800 years ago when the Dorvalans (or Perseids, as Humans call them) first used their early spacecraft to reach and colonize another planet in the Phi Cassiopeia system, the Perseid Empire has established an enviable record for both stability and growth. During the reign of Marissa III and her successors, it's something of a thorn in the Terran Empire's side, since it prevents spinward expansion... but the Perseids think of the Terran Empire the same way.
Harsh conditions on Dorvala created a society that values order, discipline, and responsibility. When the early Perseid FTL explorers returned with stories of other worlds and species - species living in primitive conditions or wracked by war and instability - the Perseids decided it was their duty to bring "civilization" to such species. For their own good, the Dorvalans conquered and annexed them, building the Perseid Empire.
The Perseids likewise believe each species belonging to their Empire has its own duty and place in the grand scheme of things. Perseids typically rule, administrate, and bring civilization to less fortunate species; another species might contribute its skill as traders, or soldiers, or agricultural technicians. Individual citizens also have a duty to contribute to the good of all; one person might do this by joining the military, another by assisting the authorities with an investigation.
While the Perseid attitude is undoubtedly arrogant, it's not oppressive. Once the Perseids consider a conquered or annexed species sufficiently "civilized;' they grant its members full citizenship and privileges in the Empire, allowing them to hold any office or attain any other benefit they can earn. (Discrimination often still occurs, of course.) While Perseid society lacks the full openness and equality of the Conjoined Civilizations Republic, it's a far cry from the despotism of the Ackalians or Thorgons.