The fearsome demon called Azzinoth was a doomguard commander of the Burning Legion during the War of the Ancients before the Great Sundering. He met his end, however, when he came upon Illidan Stormrage.
Illidan slew Azzinoth and took his weapons, a pair of vicious warglaives called the Blades of Azzinoth. Over the millennia, Illidan grew more and more adept with the demonic weapons, and likely became more proficient with them than their original owner. He carries them still.
In his duel with Arthas, Illidan mentions that Azzinoth was a "powerful demon captain".
- Azzinoth is referenced in the RPG and on the World of Warcraft website (in regards to the Blades that once belonged to him.) The event is an extension to the events of the War of the Ancients, and is not mentioned in other accounts of the War.
This has been proven to be wrong in Legion. It is most likely Azzinoth is still trapped within Illidan's body when he ate his soul, as all demon hunters must do to become one.