Rift Quest:The Beastmaster  

The den of Naveer the Primal can be found at (1200,777). As you approach this location the quest will update and the Great Summoning Whistle of Dhel will appear in your inventory. Use the whistle when your entire group is near the opening so they all get credit.

Naveer is a 20 elite with ~6500 health so bring a few good friends. After slaying him loot the Blade of Light.