The Reign of the Black King is a Quest located in New Tristram in Act I. It was shown in the 2010 GamesCom Diablo 3 Artisan Reveal, which was held in Germany. Very little is known about this quest, the objective of the quest is to Speak to Deckard Cain. It is safe to assume that this quest takes place after The Crown of Mad Leoric, Since the services of the Artisan are available to the player at that time. It also makes sense, that, once the player has mended the crown, he may seek answers from Cain.