O que há de tão especial no aço valiriano?

As principais características são que elas são mais strongs e leves que as lâminas de aço normais. Além disso, o aço valiriano foi perdido junto com Valyria, o que significa que restam apenas algumas lâminas de aço valiriano no mundo. Existem poucas pessoas no mundo que podem realmente criar uma nova lâmina a partir de uma lâmina de aço valiriana existente; tornando-os extremamente caros.

Valyrian steel blades are lighter, stronger, and sharper than even the best castle-forged steel, and feature distinctive rippled patterns similar to Damascus steel.

Only the greatest weaponsmiths can reforge swords from existing Valyrian steel, but the secret of creating such an alloy was apparently lost with Valyria, making those remaining weapons highly treasured and extremely rare. The blacksmiths of Qohor claim to know how to reforge Valyrian steel, and Tobho Mott did reforge Ice at the request of the Lannisters, in King's Landing.

A Valyrian Steel possui muitos recursos que a diferenciam do melhor aço forjado em castelo. Armas feitas de aço valiriano tendem a ser mais leves, mais strongs e mais nítidas. Também mantém sua borda melhor que o aço normal. É por isso que é um material tão desejável para fazer armas, e por que as poucas armas de aço valirianas remanescentes são altamente consideradas e transmitidas como preciosas heranças de família.

Valyrian Steel parece ter propriedades semelhantes às Damasco Steel :

Damascus steel was a type of steel used in Middle Eastern swordmaking. [...] These swords are characterized by distinctive patterns of banding and mottling reminiscent of flowing water. Such blades were reputed to be tough, resistant to shattering and capable of being honed to a sharp, resilient edge.
...
The reputation and history of Damascus steel has given rise to many legends, such as the ability to cut through a rifle barrel or to cut a hair falling across the blade. [...] Production of these patterned swords gradually declined, ceasing by around 1750, and the process was lost to metalsmiths.

As lâminas de aço valiriano são incrivelmente strongs, incrivelmente afiadas e mantêm a borda muito bem. É possível que o metal também seja criado usando feitiços. O aço é dobrado várias vezes para remover as impurezas também, similar também Damasco Steel (note que muitas propriedades de Valyrian aço são semelhantes ao aço de Damasco).

The properties of Valyrian steel are well-known, and are the result of both folding iron many times to balance and remove impurities, and the use of spells—or at least arts we do not know—to give unnatural strength to the resulting steel. Those arts are now lost, though the smiths of Qohor claim to still know magics for reworking Valyrian steel without losing its strength or unsurpassed ability to hold an edge. The Valyrian steel blades that remain in the world might number in the thousands, but in the Seven Kingdoms there are only 227 such weapons according to Archmaester Thurgood's Inventories, some of which have since been lost or have disappeared from the annals of history.
_{The World of Ice and Fire, Ancient History: Valyria’s Children}

The Daynes of Starfall are one of the most ancient houses in the Seven Kingdoms, though their fame largely rests on their ancestral sword, called Dawn, and the men who wielded it. Its origins are lost to legend, but it seems likely that the Daynes have carried it for thousands of years. Those who have had the honor of examining it say it looks like no Valyrian steel they know, being pale as milkglass but in all other respects it seems to share the properties of Valyrian blades, being incredibly strong and sharp.
_{The World of Ice and Fire, Dorne: The Andals Arrive}

Bran observa que o gelo é feitiço, escuro e afiado.

Lord Eddard Stark dismounted and his ward Theon Greyjoy brought forth the sword. "Ice," that sword was called. It was as wide across as a man's hand, and taller even than Robb. The blade was Valyrian steel, spell-forged and dark as smoke. Nothing held an edge like Valyrian steel.
_{A Game of Thrones, Bran I}

Jon observa que o aço valiriano é leve e afiado.

Jon dismounted. Slung across his back in a black leather shoulder sheath was Longclaw, the hand-and-a-half bastard blade the Old Bear had given him for saving his life. A bastard sword for a bastard, the men joked. The hilt had been fashioned new for him, adorned with a wolf's-head pommel in pale stone, but the blade itself was Valyrian steel, old and light and deadly sharp.
_{A Clash of Kings, Jon II}

As lâminas são cinza escuro e contêm um padrão de redemoinho de onde foi dobrado sobre si mesmo. Os feitiços no metal de alguma forma lembram a cor que deveria ser e as tentativas de mudá-lo geralmente se revelam infrutíferas, embora Wail e Oathkeeper da Viúva mantenham algum vermelho neles.

Tyrion wondered where the metal for this one had come from. A few master armorers could rework old Valyrian steel, but the secrets of its making had been lost when the Doom came to old Valyria. "The colors are strange," he commented as he turned the blade in the sunlight. Most Valyrian steel was a grey so dark it looked almost black, as was true here as well. But blended into the folds was a red as deep as the grey. The two colors lapped over one another without ever touching, each ripple distinct, like waves of night and blood upon some steely shore. "How did you get this patterning? I've never seen anything like it."
"Nor I, my lord," said the armorer. "I confess, these colors were not what I intended, and I do not know that I could duplicate them. Your lord father had asked for the crimson of your House, and it was that color I set out to infuse into the metal. But Valyrian steel is stubborn. These old swords remember, it is said, and they do not change easily. I worked half a hundred spells and brightened the red time and time again, but always the color would darken, as if the blade was drinking the sun from it. And some folds would not take the red at all, as you can see. If my lords of Lannister are displeased, I will of course try again, as many times as you should require, but—"
_{A Storm of Swords, Tyrion IV}