Warning: SPOILERS for Star Trek: Discovery season 3, episode 2, "Far From Home".
Star Trek: Discovery season 3 brought back the people of Coridan, who are classic Star Trek aliens who appeared in Star Trek: Enterprise but were first mentioned in Star Trek: The Original Series. After Star Trek: Discovery season 3's premiere focused entirely on Commander Michael Burnham's (Sonequa Martin-Green) arrival in the year 3188, episode 2, "Far From Home", details what happened to the U.S.S. Discovery when they arrived in the 32nd century.
The Discovery, which is commanded by Acting Captain Saru (Doug Jones), was right behind Burnham in the wormhole they used to jump to the far future. However, Michael got separated from her starship (by lightyears and one calendar year) and the Discovery instead crash-landed on an unnamed planet that threatened to consume the Starfleet vessel with parasitic ice. Saru and Ensign Sylvia Tilly (Mary Wiseman) traveled to a mining facility called The Colony to barter for the minerals they needed to repair the Discovery and they met Coridanites in the settlement's tavern. Unfortunately, the Coridanites were being oppressed by their courier, Zareh (Jake Weber), who was running an extortion racket on The Colony and stealing their dilithium.
The Coridanites Tilly and Saru encountered were Kal (Jonathan Koensgen), who was still a true believer in the fallen United Federation of Planets, and Os'ir the bartender (Lindsay Owen Pierre), who was more suspicious of offworlders. When Star Trek: Discovery season 3's trailer dropped, some Trekkers speculated that the Coridanites were actually evolved Kelpiens, the race Saru hails from, due to their somewhat similar facial features. But Kal and Os'ir introduced themselves as "Coridans", which is an alien race that has been a part of Star Trek since The Original Series season 2 episode "Journey to Babel". In fact, in that classic TOS episode, the Babel Conference that brought Ambassador Sarek (Mark Lenard) aboard the U.S.S. Enterprise was to decide whether the planet Coridan, which was known for its unlimited supplies of dilithium, would be admitted into the Federation.
Speaking of Sarek, who was dying when he appeared in Star Trek: The Next Generation, Coridan and the Babel Conference were mentioned in the TNG episode "Sarek", when the Vulcan Ambassador mind-melded Captain Jean-Luc Picard (Patrick Stewart) and shared his true, hidden feelings about his estranged son Spock (Leonard Nimoy). Coridan was again referenced during Star Trek: Deep Space Nine's Dominion War; the planet's dilithium mines were attacked by the Jem'Hadar, which made the planet a strategically important target.
However, it wasn't until the prequel series Star Trek: Enterprise that the Coridanites finally appeared in Star Trek. In the Enterprise season 1 episode "Shadows of P'Jem", Captain Jonathan Archer (Scott Bakula) and Subcommander T'Pol (Jolene Blalock) were invited to visit Coridan, which was already a warp-capable civilization with a population of 3 billion and boasted the largest shipyards in the sector. But Archer and T'Pol were captured and held for ransom by rebel forces, who were secretly supported by the Andorians, and were in conflict with the Coridan government, which was backed by the Vulcan High Command. Archer and T'Pol were rescued by a combination of their Enterprise crewmates, Vulcans, and Andorians led by Shran (Jeffrey Combs).
A few years later, Coridan joined talks to form the Coalition of Planets, which ultimately became the United Federation of Planets. However, Coridan didn't formally join the Federation until the same year the Babel Conference ratified their membership in Kirk's 23rd-century era. Still, despite being mentioned throughout every era of Star Trek, the Coridan people make rare actual appearances in episodes, and "Far From Home" is the first time the race of miners has been seen since Star Trek: Enterprise. But with the galaxy of the 32nd century in dire straits after the Burn wiped out most of the Alpha Quadrant's dilithium, it's quite possible Coridan could have a bigger role to play in Star Trek: Discovery season 3.