This is fan fiction and is purely fan made and in no way is to be taken as official lore within World of Warcraft.
During the war of the ancients the night elves were forging weapons to combat the legion. Of these weapons, one known as Belaros was forged from the fangs of 10,000 fallen servants of each dragonflight. This sword was a great weapon in the war of the ancients as the blue dragonflight empowered the wielder and allowed him to access the powers of the dragons themselves. After the sundering the sword was taken by some exiled Highborne to what would be Quel'thalas several years later, it was hidden by the highborne as a remembrance of the past and perhaps a weapon for them to use, but they couldn't access the powers it once held and entrusted it to a family later known as the 'House of Lightblade'. It was wielded by Thiaris Lightblade, who became a Runic Knight and learned secrets about the blade. During the 3rd war against the scourge and legion at Hyjal, the sword was able to take energies from the well of eternity and blast several units of the undead with the lifegiving fire of the red dragonflight, or the fiery earthy wrath of the black dragonflight, or the pure arcane nature of the blue dragonflight but it also helped with the time slowing effects of the bronze dragonflight.
It is wielded by Mortothiar Lightblade, who tries to use the light to wield it's powers. Currently the dragonflights allow him to keep the blade, believing it is within good hands, several beings have tried to take it, none have succeeded, but if they did what of the requirements?
This blade has requirements and restrictions attached, for example. You must have the strength of a tauren or stronger to lift and swing the blade. You must know the keyword to activate the powers of the blade, and you must have gone through the blood ritual to carry the blade without it returning to it's original owner.
- It is a blade wielded by a character in Server: Steamwheedle Cartel