Arcane Magic

From wow.incgamers.com

The origin of arcane magic is questionable, but it has been suggested that the Eredar consumed their own world, and in the resulting destruction magic was sent to all the various worlds connected by the Twisting Nether.

None deny the power that arcane energy can bestow upon a person willing to delve into its mysteries, but many question the wisdom of such a course. Though it was arcane magic that bestowed immortality upon the Night Elves, it was also arcane energy that caused the dissension among their kind. It was also arcane magic that drew the Burning Legion to Azeroth, and many blame the Sundering of the world on the arcane power wielded during the final conflict of the War of the Ancients.

Arcane magic undoubtedly has a corrupting influence upon all types of Elves, transforming them both physically, as evidenced by the Naga and the High Elves, and mentally. It is an addictive force, driving those who interact with it to desire more, until the use and desire for magic exceeds all other concerns.

Oddly enough, humans seem to have avoided the corruption of arcane magic so far. The Archmage Antonidas, head of the Kirin Tor of Dalaran prior to the Third War, was 71 years old and exhibited no obvious symptoms. It is reasonable to assume, however, that prolonged exposure such as the longevity of the Elves might allow, is responsible for the corruption that is evident in their kind. The lifespan of humans might simply be too short to allow the arcane energy time to incubate, infect, and corrupt the host wielding it.

Though there remains much debate over the subject, it is an unassailable conclusion that arcane magic has been integral to the defeat of the Burning Legion, both in the distant, and recent, past. Arcane magic is still used by humans and orcs, and its use has even spread to Gnomes.