Just as there were Aura Guardians, there existed Kurai Warriors. They instead drew their power from the Kurai, which is like the darker side of Aura. If Aura were to represent life, then Kurai would represent death. Both the Kurai Warriors and Aura guardians lived in a delicate balance with each other for one could not exist without the other.
Then one day, seemingly out of nowhere, a man by the name of Lord Roderick came to power. He became consumed by the power of Kurai. The delicate balance that had once existed between the two powers began to shift. The Kurai Warriors too became consumed by the overwhelming power of Kurai. They lost themselves in the ancient power and lost their humanity. Their greed and lust for power became their driving force, as they sought to conquer the world.
The Kurai warriors did not go unchallenged. Old Kurai warriors who had stayed true to their beliefs and the Aura guardians stood as the forefront to the resistance. However, the power of Kurai had grown tainted and much more powerful, and those who opposed them were struck down merciless. As the evil spread throughout the world, a dark Shadow covered the world. the reign of Lord Roderick lasted for three centuries and the balance between Aura and Kurai teetered nearly destroying the world.
It was said that the power of Kurai not only poisoned his mind, but sustained his life giving him an unnaturally long life.
The Aura Guardians fought hard to save the world from ruins but the Kurai power had grown to exceed the power of Aura. Just when all hope seemed lost, a previously unknown Aura guardian rose up from the shadow of the Kurai and wielded the power of Aura to return balance to the world. With unimaginable power he sealed the power of Kurai in a scared temple as old as the human race itself, restoring peace to the land once again. His name was Sir Aaron.
As for the temple, Sir Aaron placed a powerful seal on the temple locking away the tainted Kurai. To make sure no one released the power within the scared temple, Sir Aaron removed a piece of the Aura barrier locking the temple in time. Over many moons the temple was swallowed by the sands of time. Its location is now a complete mystery to the world.
The Kurai key is believed to be that piece Sir Aaron removed locking the temple in time. The Kurai key had been lost for many centuries forgotten by all except through stories passed down from generation to generation. The Kurai Key became a myth slowly fading over time. Or so it was told.