Illidari-Bane Shard

The shard appears to be a piece of a larger weapon. Sharp-looking runes etched into the metal glow with a menacing light.

The weapon's intended purpose isn't clear to you, but it's hard to ignore. Most of the mo'arg at Legion Hold seem to be working with fragments of the same metal you hold in your hand. Perhaps one of the weaponsmiths at Shadowmoon Village might be able to tell you more about it.