Terran Empire

Named after its founding species' home planet, the Terran Empire is one of the most powerful known forces in the Orion Arm of the Milky Way Galaxy. It maintains military bases in orbit around hundreds of planets, and has set up treaties to protect thousands more in times of need, in exchange for resources and other services.
Despite the negative connotations of the word "empire", the Terran Empire is rarely violent in its expansion, attempts to treat the people of all its acquired territories fairly, and maintains a large council with representatives from many species. This has in turn made its growth much easier, and has encouraged many struggling species to request its leadership and protection without being prompted to do so.
The greatest issue the Empire faces is its incredible slowness to adapt, allowing unethical enterprises to flourish with little to no opposition, and discouraging even the most benevolent forms of magic from being taught or purchased (although magic is technically legal on many planets). This has earned it considerable criticism from magic users and law abiding citizens alike.

Slavery
The Terran Empire has never officially condoned slavery, and makes efforts to free slave races when taking control of new planets. Unfortunately, this has done nothing to prevent the trafficking of sapient life forms such as Star Dragons within its borders. Sapient Rights activists speculate that large scale bribery is involved in the perpetuation of slave trading in the Terran Empire, as well as the Empire's reluctance to stamp out such a lucrative industry.
Some suggest that the Empire isn't just passively allowing slavery to happen, but actively encouraging the practice, by requiring that all artificial intelligences be Three Laws compliant, regardless of their proven sapience, and the sentience their actions indicate to exist. This matter has been repeatedly brought to court over the past two centuries, and remains controversial to this day.

Slave Race Rehabilitation
Species which have been extensively subjugated are given extra assistance after being freed, helping them to develop healthier attitudes toward authority, and if their culture has been wiped out by their oppressors, to develop an identity outside of slavery.
Species incapable of developing free will are given kind and fair treatment, and those who abuse their authority over them are severely punished.

Mirror Terran Empire

- Is significantly more heavily militarized than the prime version, and is actively expanding, conquering new planets very rapidly, and subjugating their people more often than not.

- Does not attempt to suppress knowledge of magic at all, and has actively attempted to utilize it in their defensive and offensive technology.

- Endorses slavery on a massive scale, and has a worryingly large and accepted slave caste.

- Experiences widespread terrorism carried out by protesters from any number of religions and downtrodden species. Anyone who can afford a house with a bomb shelter has one.

- Androids are treated no worse than slaves, in many cases better because they can be trusted to not run away or stab their masters.

- Terra is probably pretty messed up by pollution, oceans are probably dead.