Seek out Lirastrasza at the Circle of Life in Twilight Highlands.
Hello, <race>. I wish we could meet in more favorable circumstances. The world hangs by a thread, and all that the Titans have wrought may be in jeopardy.
It saddens me greatly, but my judgment is final. Deathwing - the horrific creature that was once the Earth Warder and once my friend - must be destroyed.
I have prepared a site atop the Highlands, to the west of the Vermillion Redoubt, where I can bring about his end. Seek out the Circle of Life and speak with Lirastrasza within. I will join you there.