Blackfyre

Blackfyre is a Valyrian steel sword that originally belonged to Aegon I Targaryen, which he carried during the Targaryen Conquest of the Seven Kingdoms. Afterwards it became the treasured ancestral blade of House Targaryen, carried by kings and princes.

A little over a hundred years before the War of the Five Kings, King Aegon IV the Unworthy gave Blackfyre to his bastard son Daemon, a great warrior, instead of his lawful son Daeron II Targaryen. Many thought that this was a sign that his father favored him to rule. Afterwards, he founded his own cadet branch of House Targaryen, House Blackfyre - taking its name from the sword - and himself became known as Daemon Blackfyre.

On his deathbed, Aegon IV foolishly legitimized all of his bastard children, among them Daemon Blackfyre. His lawful son succeeded him as King Daeron II Targaryen, but eventually, Daemon Blackfyre rose up in a civil war to try to replace him on the throne, known as the Blackfyre Rebellion. The sword was lost at the end of the war.

Years later, the sword is being looked for by than other than the remains of House Blackfyre, hoping to find its ancestral weapon.