Publisher: Originally TSR (1991), most recently referenced by Wizards of the Coast. Set on Athas, a dying desert world ravaged by millennia of defiling magic (arcane magic that destroys the environment to fuel itself, as opposed to the ecologically neutral “preserving” magic of druids and rangers). Ruled by sorcerer-kings, metal is scarce, psionics are common and mundane rather than exotic.
Specific source note: the element referenced for this project is Mind Lords of the Last Sea (TSR, 1996, part of the “Wanderer’s Chronicles” line) — a supplement detailing a hidden, isolated valley far north of Tyr, centered on the Last Sea (the largest body of water on Athas) and the city of Saragar, ruled by three immortal psionicist Mind Lords who mandate happiness by decree.
Reference: Wikipedia: Mind Lords of the Last Sea