Taerer in Duskwood at the portal to the Emerald Dream.
"Taerar was perhaps the most affected of Ysera's rogue lieutenants. His interaction with the dark force within the Emerald Dream shattered Taerar's sanity as well as his corporeal form. The dragon now exists as a specter with the ability to split into multiple entities, each of which possesses destructive magical powers. Taerar is a cunning and relentless foe who is intent on turning the madness of his existence into reality for the inhabitants of Azeroth."