I am trying to find out what happened to the last of the seven vials Illidan took from the Well of Eternity.
To the best of my knowledge he poured three into Lake Hyjal, one was taken by Dath'Remar Sunstrider and later used to create the Sunwell, and he gave one each to Lady Vashj and Kael'thas (later collected by PCs during The Burning Crusade).
But I can find no cannon explanation of what happened to the final vial.
The closest I can find is speculation that it was used in the Black Temple to power the source he fed to the demons to break their addiction to the legions magic (this speculation all seems to come from the warlock Green fire quest line). Has there been any confirmed in-cannon evidence pointing to it's fate (short stories, novels, comics, etc...)?