Who exactly is Deathwing on WoW

Deathwing was once known as Neltharion the Earthwarder, and was one of the great Dragon Aspects. These were dragons empowered by the Titans to guard and foster Azeroth while they were elsewhere in the universe.

However, Neltharion was corupted by the Old Gods, who tricked him into creating the Dragon Soul, and managed to get the other Dragon Aspects to add their power to it as well. However, its corruption caused Neltharion to become a horribly scarred dragon, fire erupting from his skin from open wounds.

He had thorium plating encased into his skin in order to keep the flames in check, and became an engine of destruction, calling himself Deathwing.

Eventually, Deathwing was caught and imprisoned in Tol Barad, leaving his children Onyxia and Nefarian to manage the Black Dragonflight in his absence. This imprisonment will soon end in the next expansion for WoW, Cataclysm.

Deathwing will be released and destroy the world as we know it, changing Azeroth completely while sending his elemental minions to control this post-apocalyptic world.