The Doom annihilated the powerful and sorcerous Freehold of Valyria in mere moments. History of Westeros takes a look at what it was, why it happened, and possibly who caused it.
“At its apex Valyria was the greatest city in the known world, the center of civilization.”
“Septon Barth speculated on the matter, referring to a Valyrian text that has since been lost, suggesting that the Freehold’s sorcerers foretold that the gold of Casterly Rock would destroy them.”
“It was written that every hill for five hundred miles split asunder to fill the air with ash and smoke, and fire so hot and hungry that even the dragons in the sky were engulfed and consumed. Great rents opened in the earth, swallowing palaces, temples, and entire towns. Lakes boiled or turned to acid, mountains burst, fiery fountains spewed molten rock a thousand feet into the air, and red clouds rained down dragonglass and the black blood of demons. To the north, the ground splintered and collapsed and fell in on itself, and an angry sea came boiling in. The proudest city in all the world was gone in an instant, the fabled empire vanished in a day.”
One thing that can be said for certain is that it was a cataclysm such as the world had never seen. The ancient, mighty Freehold—home to dragons and to sorcerers of unrivaled skill—was shattered and destroyed within hours.”
“Fourteen or fourteen thousand. What man dares count them? It is not wise for mortals to look too deeply at those fires, my friend. Those are the fires of god’s own wrath, and no human flame can match them. We are small creatures, men.”
“Some, wedding the fanciful notion of Valyrian magic to the reality of the ambitious great houses of Valyria, have argued that it was the constant whirl of conflict and deception amongst the great houses that might have led to the assassinations of too many of the reputed mages who renewed and maintained the rituals that banked the fires of the Fourteen Flames.”