Eye of Sargeras

From WoWWiki

The Eye of Sargeras is a gem-like artifact previously used by the dark titan Sargeras. It was found in the Tomb of Sargeras by Illidan Stormrage. The artifact was sought by both Illidan and Gul'dan, the former gaining it only through the aid of the naga, the latter being torn apart by crazed demons. It is unknown if the Eye was Sargeras's actual eye, or simply an artifact in his posession when he was "killed" by Aegwynn, although it was described by Brann Bronzebeard as "the last remnant of his withered form".^{LoM 69}

The Eye of Sargeras was used by Illidan in an attempt to destroy the Frozen Throne, but the intervention of Malfurion and Maiev destroyed the Eye instead.