The Dragon War

The Dragon War began after the Lords of the Fae loosed their new creation upon the world, in retribution for the elves' hunting and consuming the lesser fae to empower themselves. It was not enough that the elven civilisation was almost completely destroyed in the aftermath of the Lords' strike upon their Great Ritual; the Lords intended that the elves be scoured from existence entirely.
The dragons that were released from the falling mountain spread out from the centre of the devastation, killing massive numbers of survivors before any defense could be mounted, or even reliable information gathered about what had happened. Dragons would swoop from the sky and wipe entire settlements out with little to no word of what happened, only the rubble bearing mute witness to the attacks.
Eventually, the remnants of the surrounding kingdoms managed to gather their forces together sufficiently to start to fend off the attacks. Entire orders of monster hunters and knights were founded, leading whole armies as they struggled to find ways to kill the massive predators. Thousands of warriors were lost in combat, but each encounter provided more knowledge about the strengths and weaknesses of the different types of dragons. After enough time had passed, the dragon hunters began to win more battles than they lost, and the numbers of dragons began to be whittled down.
The dragons were not intelligent enough to realise what was happening, but they were still horrifying opponents, causing indiscriminate loss of life. It took many years of warfare before they were beaten back to the former ritual site, now known as the Mountains of the Sky. They have taken root there, impossible to destroy completely, but mostly contained. Unwary ships and villages around the edges of the Wyrmsea are still lost periodically, but in vastly lesser numbers than they were nine hundred years ago, before the Dragon War was declared officially over.