Spirit of Destiny
The Spirit of Destiny is an undefined, intangible entity that cannot be contained in a single vessel.
Before Arthur Pendragon drew Excalibur from the Stone of the Sword in 500, the Spirit of Destiny announced in Londontown, "Whosoever pulleth this sword from this stone will become King of Britain." 
In April 1951, the Spirit of Destiny spoke with Macbeth mac Findlaech at Arbroath Abbey after repairing the damage the Stone of Scone encountered when it was stolen from Westminster Abbey the previous Christmas. ("Rock of Ages")
Later that November, David Xanatos and the Illuminati both attempted to capture the Spirit of Destiny by stealing the Stone of Destiny as it was en route from Westminster Abbey to Edinburgh, while Arthur sought to protect it. However, the Spirit spoke to each of these individuals telling them that their efforts were pointless.
The Spirit of Destiny claimed to be the Fatal Stone; the Lia Fáil; the Stone of Bethel and Jerusalem, and of Egypt; Samothrace and Portugal; the Stone at Tara and of Mora; at Iona and of Scone; the Blarney Stone; the Coronation Stone; the Hero Stone; the Philosopher's Stone, the Standing Stone; the Cornerstone; the Foundation Stone; the Megalith Dance; the Burden of Sisyphus; the Rock of Gibraltar; the Pillars of Hercules; Uluru; Clach sgàin; Jacob's Pillow; the Rosetta Stone; the Rune Stone; Sire of the Wyrd; the Mantle of Fate; the Stone of Destiny; and the Rock of Ages.
It also said that no mere mortal can possess it.
Voice Actor: Frank Welker