Forgotten Soul

Forgotten Souls are a high-level crafting material in Diablo III, obtained by using the Blacksmith to salvage legendary or set weapons and armor. Each item salvaged with an item level of 61-70 will yield 1 Forgotten Soul. A Rift Guardian may also give up one of these upon defeat for players in the level range of 61-70. This material is the higher tier version of the Fiery Brimstone crafting material, and it is used in crafting legendary and set items of level 61-70, as well as enchanting those items.

Forgotten Souls are account bound (BoA), and they can be stacked up to a maximum of 1000. They are the chief bottleneck for all end game crafting and legendary enchanting, and most players feel it is impossible to have too many, since at any moment a ring or amulet might require a dozen or more enchants to get the perfect affix.