Unless they've changed something since The Dark Below, the primaries were only available from Heroic Crota's End. Oversoul Edict could be obtained from the Abyss, Abyss Defiant from the Bridge, and both Fang of Ir Yut and Word of Crota were from Crota himself. On Normal mode, armor could be obtained from the Abyss, Bridge, and Crota while Special and Heavy weapons were only from Crota. The class item was obtainable from a simple chest in the Abyss at first, but was changed to Ir Yut, whose loot acted similarly to a chest and was only available once regardless of difficulty. Radiant Materials could drop from any encounter and dropped from all chests. Exotics were possible drops from Ir Yut and Crota.