Archaria III was a planet located somewhere in the space of the galaxy's Alpha or Beta Quadrants, the third planet in orbit of the Archaria star system. Archaria III was a colony of the United Federation of Planets.
Archaria III was settled by a group of religious zealots know as the The Brotherhood in 2102. Seven years later they encountered Peladians settler who colonized the planet at the same time. It grew to become a joint colony of Humans and Peladians by the 24th century. Its history was riddled with interspecies conflict ranging from wars and assassinations through racism.
Archaria III was hit by a mysterious plague in 2364.
By the 24th century a religious group known as The Purity League would preach the belief of wrongfulness of interspecies mating and would refer to them as mixers. These individuals would be regarded as second-class citizens.
Tough officially such prejudices would be prohibited by law but in backwater towns discrimination still ran rampant. Only in the major cities would Humans and Peladians work and live together in something resembling harmony. In more rural settings, things were so bad that full-blooded Peladians lived in isolated enclaves surrounded by their own kind.
Those with "mixed" heritage relocated to the large cities in record numbers, but after the plague of 2364, they fled back to the country were they lived as vagabonds in tent camps. It was estimated at the time that the population of "Mixers" ranged from 150,000 to 200,000. (TNG novel: Infection)