Sealing the Blade
Defeat Heolstor, Warden of Oryx, and then Alak-Hul, the Darkblade, within 30 seconds to seal your Void Edge.
"The Wardens you seek are infamous devourers of the Light. Each has its own heinous preference. Together, they guard the Sunless Cell, where Alak-Hul, the Darkblade, languishes." —Eris Morn