Andrew Brownell wants you to kill Amnennar the Coldbringer and return his skull.
Quest Text Edit
In the Barrens lies a horrid mess of tangled vines called Razorfen Downs. While our first observations of this place revealed little threat, our recent findings are much more serious...
The quilboar of Razorfen Downs have aligned themselves with the Scourge. A Lich named Amnennar the Coldbringer rules them now, using the power of his massive consciousness to control their every move.
Amnennar has a direct telepathic link to Ner'zhul; we must sever this bond, <Name>. An end must come to the Coldbringer.
Oddly enough, the objective location is displayed as being in Tirisfal Glades near Agamand Mills on the world map.