Back story of the Engram Crota has been trying to forge the power of the engrams to allow his knights to wield the ultimate weapons. Unfortunately all attempts have been a fail for the engram only comes out uncommon and rare. After three days of ritual and preparations. He Succeeds, behold that black engram but right as he finishes, BLAM we bust through the door and the raid begins. The black engram is a drop from Crota during the Raid but is extremely rare. The Black Engrams allows you to choose an exotic you'd like.