The Sword of Gryffindor was a thousand-year-old, goblin-made magical sword owned by the famed wizard Godric Gryffindor, one of the four founders of Hogwarts School of Witchcraft and Wizardry.

The Sword of Gryffindor was made in the 10th century by goblins, the magical world's most skilled metalworkers, and was therefore enchanted. Fashioned from pure silver, it was inset with rubies, the stone that represented Gryffindor in the hour-glasses that counted the House points at Hogwarts. Godric Gryffindor's name was engraved just beneath the hilt.

The sword was made to Godric Gryffindor's specifications by Ragnuk the First, finest of the goblin silversmiths, and therefore King (in goblin culture, the ruler did not work less than the others, but more skillfully). When it was finished, Ragnuk coveted it so much that he pretended that Gryffindor had stolen it from him, and sent minions to steal it back.

Gryffindor defended himself with his wand, but did not kill his attackers. Instead he sent them back to their king bewitched, to deliver the threat that if he ever tried to steal from Gryffindor again, Gryffindor would unsheathe the sword against them all. The goblin king took the threat seriously and left Gryffindor in possession of his rightful property, but remained resentful until he died.

The story persisted, in some sections of the goblin community, that Gryffindor actually stole the sword from Ragnuk. This was a result of the cultural understanding of ownership that goblin-made items rightfully belonged to goblins, rather than the heirs of those who may have purchased them, a cultural understanding that should have been honoured by the wizards.

Physical Appearance
The Sword of Gryffindor was made of pure silver, and its hilt was set with egg-sized rubies - the gemstone that was used to symbolise the House of Gryffindor at Hogwarts. The full name of Godric Gryffindor was also engraved just beneath the hilt.

Magical Properties
Much like a wand, the sword of Gryffindor appeared to be almost sentient, responding to appeals for help by Gryffindor's chosen successors. Whenever a "true Gryffindor" needed it, the sword would let itself be pulled out of another of Godric Gryffindor's artefacts - the Sorting Hat. After Ron Weasley saved him from drowning, Harry believed that since it was Ron who recovered the sword it was Ron who had to use it because "Dumbledore had at least taught Harry something about certain kinds of magic, of the incalculable power of certain acts". In addition, the portrait of Dumbledore told Severus Snape that the sword must be taken under conditions of need and valour, which was why Snape put it into the frozen pond in the first place.

As goblin's silver, it imbibed only substances which strengthened it, which could then be used against enemies. This means that it never required cleaning. Due to Harry Potter killing the Serpent of Slytherin with it, the sword was imbued with Basilisk venom and could destroy Horcruxes.

Source: Fandom