Can't Loot Corrupted Essence

If you have already looted Oakheart this week prior to picking up Darkheart Thicket: Fallen Power, you will need to wait until the weekly reset to get the item.

You must loot Corrupted Essence from Oakheart's corpse, as it is not automatically pushed to your inventory, and you won’t receive it in the mail. This quest can only be completed on Mythic difficulty—Normal, Heroic, and Mythic+ will not count.

Note: Game Masters will not provide the quest item or quest credit.