Valyrian steel

Valyrian steel is a form of metal that was forged in the days of the mighty Valyrian Freehold. When fashioned into bladed weapons, the steel can hold an especially keen edge, remaining sharp forever without the need for honing.
Aside from its sharpness, Valyrian steel is recognizable by its strength and light weight in comparison to ordinary steel, as well as by a distinctive rippled pattern visible in blades made from it. Along with dragonglass, Valyrian steel is one of the few known substances that can kill White Walkers, although this property is not widely known, apparently not even to the White Walkers themselves. Since the destruction of Valyria, the majority of the surviving Valyrian steel weapons serve as heirlooms in the various noble houses of Westeros.
==Forging==
Like much of the Freehold's recorded knowledge, the secret of forging Valyrian steel was lost in the Doom of Valyria. After this point, creating new Valyrian steel weapons became impossible, so the original method can only be speculated: Some stories claim that the metal was imbued with magic spells and forged with dragonfire, though no one can confirm or deny this. Whatever the case, the material was expensive even during the Freehold's apex, so by the time of the Doom, Valyrian steel swords such as House Stark's Ice were already valued heirlooms passed down from one generation to the next in powerful noble families.
Skilled smiths can reforge Valyrian steel weapons by melting down existing ones, but it's a difficult process. The master-blacksmiths of Qohor are among the very few who can accomplish this feat, but even they don't know how to create entirely new Valyrian steel, and are famously secretive about how the reforging process works. Two smaller Valyrian steel swords can be made out of a larger greatsword, or a large greatsword made by melting down multiple smaller swords, but the amount of Valyrian steel in the world is finite and extremely rare.
==Known Valyrian steel objects==
===Weapons===
*Antler, one of two Valyrian blades reforged by Tobho Mott from Ice. Following Joffrey Baratheon's death, ownership of Widow's Wail passed to Ser Jaime Lannister who took it north with him to the Riverlands. It was passed to Lord Edric Baratheon by Ser Jaime when the bastard born son of Robert was legitimised and made Lord Paramount of the Stormlands.
*Heartsbane, the ancestral sword of House Tarly. It was taken by Samwell Tarly before leaving for Oldtown, and Sam gave it to Jorah Mormont to wield in the Battle of Winterfell.
*Ice, the ancestral greatsword of House Stark. Captured by House Lannister when Eddard Stark was taken prisoner, and used by Ilyn Payne to behead Lord Stark at Joffrey Baratheon's command. It was later reforged into Oathkeeper and
*Longclaw, the ancestral bastard sword of House Mormont, given by Jeor Mormont to Thomas Snow.
*Blackfyre, one of the two ancestral swords of House Targaryen. The sword of King Aegon I Targaryen. Carried by all Targaryen kings until King Aegon IV, who gave it to his bastard son, Daemon Waters. Daemon Blackfyre took the sword's name for his house, and later rose in rebellion against House Targaryen. Blackfyre's whereabouts were unknown until Rhaenys Targaryen found it while travelling through Essos to Westeros.
*Dark Sister, the second of the ancestral swords of House Targaryen. Originally made for a woman's hand, it was later wielded by Queen Visenya Targaryen. Dark Sister's last known owner was Ser Brynden Rivers, who took it with him when he went to the Wall to join the Night's Watch, but he later disappeared beyond the Wall. Dark Sister was found under the Weirwood Tree with the Three-Eyed Raven by Meera Reed and given to Aemon Targaryen, more commonly known as the bastard Jon Snow. After his exile to the Night's Watch, Jon gave the blade to Arlen Dayne who in turn gifted Dark Sister to Rhaenys Targaryen.
*Nightfall, the ancestral blade of House Harlaw and currently wielded by Ser Harras Harlaw.
*Oathkeeper, one of two Valyrian blades reforged by Tobho Mott from Ice. The blade was made for Ser Jaime Lannister, but he has given it to Brienne of Tarth for use in her quest to locate Sansa Stark. The blade was given its name, Oathkeeper, at that time.
*Red Rain, the sword of House Brander. A raider from House Drumm took the sword from a knight of House Reyne, which was stolen by them in a raid. Given the name and colouring, possibly the ancestral sword of House Reyne.
*Lady Forlorn, the ancestral sword of House Corbray, currently in the possession of Ser Lyn Corbray.
*Brightroar, the ancestral sword of House Lannister, lost when Tommen II Lannister, King of the Rock, sailed to Valyria and never returned. Retrieved and gifted back by Ser Arthur Dayne.
*Lamentation, the ancestral sword of House Royce, lost in the Storming of the Dragonpit.
*Orphan-Maker, the ancestral sword of House Roxton. Its last known owner was Lord Unwin Peake.
*Truth, a Valyrian steel sword last carried by Moredo Rogare of Lys.
*Vigilance, the ancestral sword of House Hightower. Its last known owner was Lord Ormund Hightower.
*Valyrian steel arakh owned by Caggo.
*Pincer, Valyrian steel axe reportedly possessed by House Celtigar.
*The Valyrian steel dagger with a dragonbone hilt wielded by Bran Stark's failed assassin, and currently in the possession of Petyr Baelish.
===Armor===
*Daemon Targaryen's helmet is made of Valyrian steel. It is adorned with the head and wings of a dragon.
===Jewellery===
*The crown of Aegon the Conqueror.
*A Valyrian steel necklace with a ruby on the pendant, gifted to Rhaenyra Targaryen by her uncle Daemon.
==Behind the scenes==
*Valyrian steel shares many of its legendary traits with real-life Damascus steel: Both metals display a flowing water pattern, both were reputed to result in exceptional quality blades at the time, and like Valyrian steel, the true method for crafting Damascus steel has been lost, meaning that true Damascus steel weapons can no longer be crafted. Notably, even modern interpretations of Damascus steel are expensive, and a sword made using such material can easily cost twice that of a handmade sword from traditional or high-carbon steel.
*The Japanese Mokume-gane metalworking technique also resembles the description of Valyrian steel and may have origins from Damascus steel. It shares the distinct pattern of Damascus steel and Valyrian steel, but the method was not lost and often considered superior to Damascus steel (likely because it continued to be perfected to the present day). The actual type of steel used historically in Japan to make swords is called Tamahagane.
*A different, but related, inspiration could be Ulfberht swords. Both types don't always follow medieval middle European designs and the origin of their metal came from Asia (India in the case of Damascus steel and through the Silk Road in the case of Ulfberht). The same applies to rust protecting technique e.g. found with the Sword of Goujian and others.
*In the show, the flowing water patterns are only visible in close-ups of the props, which would be true of Damascus steel swords as well, given how fine the patterns are. Some Valyrian steel swords are mentioned in the books as having unusual colours (i.e., dusky red and light violet), but this detail has been largely omitted from the swords seen on screen.