We've all heard the tales of the grandmothers meant to scare their children to their beds; tales of creatures that live in the dark places, the cruel G'lins, stories of foul Nogmes who trick young mothers to giving them their newborns with illusions, tales of barbarous Trolls who lure warriors in challenges to never be seen again, not to mention the Xies who tempt great men to the depths of silt pits with the promise of lust. These are all tales with truth in them; tales from the old days of Athas.
What happened to these fabled creatures? These races, along with the lion like wemic, the vicious orcs and the noble high-g'lins died so that we may live. The demons of old infested these noble races and turned them against us even as they fought for us. Even though the old races were corrupted the High Kings found ways to rally them to our cause, to convince them that the demons were the real enemies, for not all of the race was corrupt.
Wars were raged for generations. The demon plague was seemingly unstoppable, kingdom after kingdom was ravaged and our protector races fell to corruption in total in addition to many forces of the fair races, the humans, elves, and dwarves. And as the demons inched closer to our realms their taint and corruption spread to our races. These abominations were worst of all. The clan of the Trollmoors once famed human warriors corrupted to evil brutes. The elves of the Wemi planes, elves who befriended lions and used them as mounts were desecrated by being merged with their sacred animals to become Wemics. It was during these wars that the half-giants were made. The noble high-glins had become horrible creatures called hob-goblins and led much of the battles. Once proud orcs now fought us tooth and nail with an uncivilized rabidness never before seen. And it was decided that these abominations must be cleansed.
Again the wars raged on, but the High Kings were victorious , the last of the corrupt races were put down. It was with heavy hard that several of the High-Kings realized they must protect their own people from the corruption and to do this champions must be created to do what they themselves could not. To this end, Borys Butcher of Dwarves, Albeorn Elf Bane, and others were created to remove the Taint of evil from the pure races.
Once the corrupt portions of the races were exterminated and the lines of battle held, the High-Kings created the Periphery to hold the demons at bay indefinitely. For a time there was relative peace or at least the siege mentality faded, but the High-Kings were brought back to the mindset of war and heavy decisions as one of their own fell to the corruption of the other realms. The High-King Daskinor mind was eroded by his struggle against the taint. He began having delusions and in the end used magic and psionics to allow strange aberrations into Athas from the outer realms. Keltis, High-King of Kurn tried to help his brother, but could not.
Fearing Daaskinor's abominations would siege the other cities Keltis drew his own Periphary between the cities of the north and the cities of the Tablelands, thus Kurn and Eldaarich became the Lost Cities of the Forgotten North.