The Doom of Valyria

In a single night the Freehold that had ruled half the world was unmade: the Fourteen Flames burst, the peninsula shattered, and every dragonlord within reach died with their dragons. What caused it, no one living knows. House Targaryen survived only because twelve years earlier a girl named Daenys had dreamed the ending and her father had been strange enough to believe her, and moved the family to a rock called Dragonstone.

The fuller tale

The Freehold of Valyria had ruled half the world for five thousand years, and then in a single night it stopped. The Fourteen Flames ÔÇö the volcanic range the whole civilisation was built on and mined with slaves ÔÇö burst together. The peninsula shattered into islands. Fire and ash took every city within reach, and the sea came in behind it. Every dragonlord who was at home that night died with their dragons.

Nobody knows why. The theories are all unsatisfying in different ways: that the mines went too deep; that a rite went wrong; that the slaves of the Fourteen Flames did something no one recorded; that the gods simply had enough. The one thing the maesters will commit to is that it was not gradual, because the records of forty client cities stop in the same week.

House Targaryen survived by an accident so improbable it has been read as prophecy ever since. Twelve years earlier a girl named Daenys had dreamed the ending, and her father Aenar ÔÇö a dragonlord of the fortieth rank, nobody important ÔÇö had been odd enough to believe a daughter's dream, sell everything, and move the family and five dragons to a rock in the narrow sea that no one else wanted. Valyria laughed at him. Valyria is a smoking sea.

The century that followed

The Doom did not end the world; it removed the thing holding it down. What followed in Essos is remembered as the Century of Blood. Volantis declared itself the Freehold's heir and made it stick for two generations before the other Free Cities and a Westerosi sellsword prince broke the attempt. The Dothraki, who had been kept in their grass by the simple fact that Valyria had dragons, were united under a khal named Mengo and came off the steppe. The Kingdom of Sarnor ÔÇö ancient, wealthy, unable to agree on anything ÔÇö was taken apart city by city and is now a list of ruins on a map.

In Westeros almost nobody noticed. The Seven Kingdoms went on quarrelling among themselves for another hundred years, until the great-great-grandson of the odd man who had believed his daughter came ashore at the mouth of the Blackwater with three dragons and a small army.

What was lost with it

Valyrian steel cannot be made any more. Not one smith in the world knows how, and the swords that exist are counted and named. The roads the Freehold drove still run straighter and truer than anything built since, and no one can build another. The tongue survives as nine bastard dialects in nine cities. That is what a civilisation looks like a century after it ends: better roads than the people using them can make, and a language nobody speaks properly.

Elsewhere in the wiki

 See the world as it stood in 102 BC 

What became of it ÔÇö if an ending is written, it is here. Spoilers.

The chronicle records no ending here ÔÇö or none the maesters have set down.