This article or section includes speculation, observations or opinions possibly supported by lore or by Blizzard officials. It should not be taken as representing official lore.
It is believed that by some that the Illidari appear to be a Faction in the mold of the Alliance, Horde, Scourge, or Burning Legion that encompasses the entirety of Illidan's forces. Some believe Illidari may be an adjective form for Illidan's forces. Others believe that it is perhaps a title given to specific members of Illidan's forces. As a title, this appears to be used mostly with his demonic minions.
However, Illidan's Naga and the blood elves under Kael'thas use their own unique banners and tabards rather than those of the Illidari, which may suggest that they are not actually part of the Illidari itself.
Most appear to be found in Shadowmoon Valley and the Black Temple. This suggests that the "Illidari" may be an inner circle of forces who are closest to Illidan and certain leaders, and perhaps form an elite guard.