The Age of Dragons
The Freehold remained a great power on the eastern continent of Essos until approximately 400 years ago, its great families wedding sister to brother to preserve the important bloodlines. It was at this time that some great cataclysm befell it, known to all hereafter as the Doom of Valyria, shattering it with fire and ash. What had taken millennia to build was destroyed in a day.
This catastrophic event resulted in the destruction of the Valyrian peninsula, turning the strait into the Smoking Sea. It is said that the decline of magic occurred either with the Doom or some time before it. The survivors of the Doom fled on ships. One family of high lords, the Targaryens, had settled upon Dragonstone 100 years previously, and so it is that the Targaryens and their dragons arrived on Westeros, lead by Aegon I “the Conqueror”.