Some of the essence quest have had their items bugged since their reintroduction. It says that the item isn't found yet, except i've already previously picked up the required item (for example Ehrath'Ur's Horned Wreath). This stops me from completing multiple essence quests on the moon, making multiple weapons/armor pieces unobtainable for me.
I have tried to do obtain the quests on other characters, that had not previously obtained/completeled the bugged essence quests. However the item is not able to be obtained there either.