The Dragon Overlords
The immediate aftermath of the Chaos War was hard for the people of Ansalon but they hardly had time to recover when a new and terrible threat was upon them.
Dragons both good and evil had played a pivotal role in the history of Krynn. The evil White, Black, Green, Blue and Red Dragons (or 'Chromatic Dragons' collectively) served the goddess Takhisis in her many attempts to take over the world. The noble Brass, Copper, Bronze, Silver and Gold Dragons (or 'Metallic Dragons' collectively) had been loyal the good god Paladine and had always opposed her.
The dragons of Ansalon were every bit as lost and upset by the departure of the gods as the humans, elves and other two-legged peoples. When rumours began to appear of the appearance of an unknown red dragon, larger and more powerful than any yet known many chromatic dragons dared hope it was Takhisis returning.
They were fatally wrong.
Malystryx the Red was an enormous dragon from some unknown land across the eastern ocean. When she arrived in Ansalon in 1 SC she began a reign of terror not just against the local humans and kender but against her fellow dragons, dozens of whom were slaughtered by the titanic creature. Through some alien magic Malystryx (or Malys as she is also called) was able to draw power from the slain dragons to shape the very lands around her, turning the fertile forests and hills of Balifor and Kendermore into a region of volcanoes and ash desert known as the Desolation.
Other dragon overlords appeared over the next few years. Khellendros the Blue ('the Storm over Krynn') took over much of northern Solamnia, creating the desert like Blue Wastes. Onysablet the Black ('Sable') conquered the eastern shores of the New Sea, turning much of it into the vast New Swamp. Gellidus the White invaded Southern Ergoth, turning that large temperate island frigid and beset by gales. Beryllinthranox the Green ('Beryl') conquered the elven forest kingdom of Qualinesti and began increasing the spread of the forests into what had once been plains.
Eventually the Dragon Overlords declared an end to the Dragon Purge. The weaker surviving chromatic dragons now serve the Overlords as minions while the surviving metallics remain in hiding. More than half of Ansalon lies uneasily under draconic rule, the inhabitants forced to pay tithes and live on the sufferance of their immense masters.