Calibrax

Calibrax was the enchanted sword associated in Prytanian myth with the legendary King Urtur, who used the magical blade to unite the folk of Prytania against both the Seaxnas who were invading from foreign shores and the forces among their tribes that threatened to tear their civilization asunder.

Legend holds that Calibrax was forged in ancient times from star-metal that fell from the sky (some sort of meteoric iron and other strange materials blended into an odd alloy). It was forged with the help of fairy people (including the elven priestess known as The Lady of the Lake), and so was clearly not true iron.

It was once wielded by a Prytanian-Norrani noble remembered as Macsen (Maximus), who bore it from the island in a failed attempt to seize the Norrani Imperium. It was recovered centuries later by the druidic magician known as Myrddyn, and brought back to Prytania to be wielded by Uthyr, the prince that Myrddyn hoped to make High King of all Prytania. When Uthyr failed and died, he plunged Calibrax into a boulder, declaring that none could draw it forth but the High King. Thus it became known that whoever could draw the sword from the stone would be fated become High King of Prytania.

Myrddyn had Uthyr's son Urtur (later King Urtur) raised in secret until he could draw forth Calibrax and rule as High King of Prytania. As long as King Urtur bore Calibrax, he seemed invincible in battle. It is told that at least once, he abused its power and the sword broke, and had to be returned to The Lady of the Lake to be repaired. Once repaired, The Lady of the Lake returned Calibrax to King Urtur, who bore the blade for the rest of his life.

As King Urtur lay dying on his final battlefield, he commanded that Calibrax be returned to The Lady of the Lake, to be kept safe against the day when the enchanted blade would be needed for the defense of Prytania once again.

Appears in: "Old Blood, Bright Fire" (in Tales from Midhgardhur, Volume I)

Source: Based on the legend of the sword Excalibur from Arthurian Mythology