De acordo com O Mundo do Gelo e do Fogo, o Aço Valiriano começou a vir a Westeros propriamente cerca de 200 anos antes da Conquista, mas já estava nos Sete Reinos antes disso.
Perhaps in preparation for their crossing of the narrow sea, the Valyrians also established their westernmost outpost on the isle that would come to be known as Dragonstone some two hundred years before the Doom. No king opposed them—and though the local lords of the narrow sea made some effort to resist it, the strength of Valyria was too great. With their arcane arts, the Valyrians raised the Citadel at Dragonstone.
Two centuries passed—centuries in which the coveted Valyrian steel began to trickle into the Seven Kingdoms more swiftly than before—though not swiftly enough for all the lords and kings who desired it. And although the sight of a dragonlord flying high above Blackwater Bay was not unknown, it occurred more frequently as time passed. Valyria felt its outpost was secured, and the dragonlords thus continued their schemes and intrigues on their native continent.
The World of Ice and Fire, Ancient History: The Doom of Valyria
Sam lê sobre dragonsteel em um livro onde o último herói matou um outro com uma lâmina feita do material. Embora não esteja claro se o aço de dragão é o aço valiriano, Sam e Jon parecem pensar que é.
"The armor of the Others is proof against most ordinary blades, if the tales can be believed," said Sam, "and their own swords are so cold they shatter steel. Fire will dismay them, though, and they are vulnerable to obsidian." He remembered the one he had faced in the haunted forest, and how it had seemed to melt away when he stabbed it with the dragonglass dagger Jon had made for him. "I found one account of the Long Night that spoke of the last hero slaying Others with a blade of dragonsteel. Supposedly they could not stand against it."
"Dragonsteel?" Jon frowned. "Valyrian steel?"
"That was my first thought as well."
A Feast for Crows, Samwell I
Note que quando Daenerys promete uma espada de aço valiriana para Sor Jorah Mormont, ela menciona a forja de dragão separadamente. Isso poderia significar que o aço valiriano é essencialmente apenas uma marca de aço de dragão e, assim, o aço valiriano nunca foi testado antes, mas diferentes versões dele foram.
She nodded, as calmly as if she had not heard his answer, and turned to the last of her champions. "Ser Jorah Mormont," she said, "first and greatest of my knights, I have no bride gift to give you, but I swear to you, one day you shall have from my hands a longsword like none the world has ever seen, dragon-forged and made of Valyrian steel. And I would ask for your oath as well."
A Game of Thrones, Daenerys X
Isso, ao lado do fato de que obsidiana foi testada e provada contra os Outros e é conhecida como dragonglass, provavelmente lhes dá razão suficiente para acreditar que pode matar um Outro.
And then he was stumbling forward, falling more than running, really, closing his eyes and shoving the dagger blindly out before him with both hands. He heard a crack, like the sound ice makes when it breaks beneath a man's foot, and then a screech so shrill and sharp that he went staggering backward with his hands over his muffled ears, and fell hard on his arse.
When he opened his eyes the Other's armor was running down its legs in rivulets as pale blue blood hissed and steamed around the black dragonglass dagger in its throat. It reached down with two bone-white hands to pull out the knife, but where its fingers touched the obsidian they smoked.
A Storm of Swords, Samwell I