Drow

Drow, like High Elves, are not infact descendents of the Tel Quessir like most elves believe. The drow instead are descendents of the fey of the Seelie Court (or Summer Court as it is sometimes known). Courtiers of Araushnee, the fey of the Seelie Court were banished from The Feywild along with their goddess, from then on known only as Lolth. Cursed to hide from the sunlight they once treasured, they fled to The Material Plane they once coveted. But instead of ruling over The Forest as they planned, they were forced to flee underground into the depths of the Underdark. Many drow attempted to settle close to the surface, but were unable to compete with duergar for land or resources, and were forced to rejoin their main cohort in the deepest caverns.
Here, guided by an embittered Lolth, the drow strove to build an empire to match their goddess' fabled plans. Prioritising progress and evolution, the drow lived harsh lives carving out their settlements by force, driving out the mindflayers, deep gnomes, and other races who had long claimed in the most advantageous locations for their own. Though comparitively resource-rich, these locations were still scarce for food and other basic necessities, so (at the advice of their goddess) they turned what plentiful resources they had into methods of extracting those resources from others. Metal and stone built vast unassailable cities, then in turn became great war machines to expand those cities and overwhelm nearby settlements. Once a competing settlement was overwhelmed, Lolth commanded it's resources be used in the most efficient manner, with no care for ethics or compassion. And so, these cities built on the blood and suffering of the drows' hardwork instead became powered by the enslavement of prisoners of war and the pillaging of more productive communities.
Drow did not naturally believe this was the right way to build a successful society, but those who spoke out too vocally in support of social change were met with harsh punishments from Lolth, until it wasn't necessary for her to step in and the drow would police themselves, shaming those who disagreed with Lolth's "wisdom" and enacting punishment themselves. Many other drow who didn't agree with the practices stayed silent out of fear, or because the desperation of surviving in such inhospitable territory made them selfish in their priorities. Over the thousands of years, drow society adapted, public opinion always being spun and twisted by Lolth, until the systems of oppression were engrained into drow cultural norms and beliefs, and even those who did not outwardly support the racist and imperialistic regime unconsciously reinforced it's power with biased beliefs and actions.