Dreadknights were level 63 elite nathrezim that randomly appeared from the Dark Portal in the Blasted Lands during the Dark Portal Opens event.
Once a dreadknight spawned, elite NPCs would also spawn and rush the portal. These spawned NPCs could include Melgromm Highmountain, Lord Marshal Raynor or Justinius the Harbinger.
Yells: Quake, mortals! Quake and kneel before your destroyer.