Short answers, pulled from the story.
Dark Sun is a Dungeons and Dragons campaign setting set on the post-apocalyptic desert world of Athas. The original Dark Sun Boxed Set was released in 1991 for the second edition of D&D and became one of TSR's most successful releases of the 1990s.
TSR ended the Dark Sun line abruptly in late 1996, signaled by the absence of any Dark Sun products in the schedule published in Dragon magazine issue 236. No official reason was stated publicly. The final release was Psionic Artifacts of Athas, and at least two sourcebooks were rumored to be near completion at the time.
Artist Gerald Brom stated that he "pretty much designed the look and feel of the Dark Sun campaign," producing paintings before the designers had written the setting, with designers then incorporating his images and characters into the world. The broader design team included Rich Baker, Tim Brown, Troy Denning, Steve Winter, and others.
Athas has no gods, no traditional clerics, and no metal-based economy. Arcane magic destroys the environment when cast and is widely despised. Psionics are common to nearly all living creatures. Standard fantasy races such as trolls and goblins were exterminated in ancient wars, and races like elves and halflings are radically different from their counterparts in other settings.
No official fifth edition Dark Sun product has been released. Wizards of the Coast has chosen not to reissue the setting due to its ingrained controversial content, including slavery, genocide, and racial savagery. Developer Mike Mearls mentioned the setting at Gary Con in 2018 in connection with planned psionic rules.
The Prism Pentad is a five-novel series written by Troy Denning and edited by James Lowder, beginning publication in 1991 alongside the original Dark Sun Boxed Set. The novels were tightly coordinated with playable adventure modules, making Dark Sun the first TSR setting to ship with an established metaplot already in place.