Shadow Essence

Shadow Essences were a type of Essence acquired during Diretide 2012, Diretide 2013, and Frostivus 2012. Up to one could be socketed into a single Greevil Egg (overriding previously socketed Essences) to create the black-colored "Dreaded Greevil" courier. They could also be used in Diretide 2013 crafting recipes.