It is said that while the creatures of the world spent eons within the garden of Lunara, the Other Race was busy fighting amongst themselves. When Alara and her followers returned to the world, it was in a state known as the Wasteland. It is rumored that the Other Race created this state with something known as the Annihilation Crystal.
This object was a gigantic poisonous stone that grew in the center of the Underworld. It's energies were channeled and used to taint the land until it was completely blighted into the Wasteland. When Alara used the Vial of Terra to rectify this damage, the Annihilation Crystal was shattered and pieces of it were thrown into the far reaches of the Underworld, making it impossible to reunify.
However, it has been said that some of these pieces are large enough to still recreate the blighting effect and that one may have been discovered beneath the city of Darkness.
Where the Annihilation Crystal first appeared, or how it was created is still a mystery. However, some suspect that a rumored God known as Balor may played a major role in its origination, and the people who believe this rumor have begun to call the crystal "the Eye of Balor."