Rift Quest:Reaping the Whirlwind  

This is much easier than it sounds. Head south from Camp Vigil and you will see an Air rift on the right of the path with a statue-thing in the middle. Naga's and large birds surround it. Pick a mob and use the Sigil of the Stormbreaker. It will kill them instantly. Pick carefully and clear a path to the middle killing at least 6 on the way, then click the reliquary to seal it!

The sigil does NOT vanish when you kill the sixth mob so don't worry you will lose your weapon this time.