I was doing the quest to be able to summon Anzu, in Setthek Halls Heroic, but when I took the quest, the NPC gave me a bag containing a letter and the item to summon the boss.
I can take the letter out of the bag, but the moonstone remains in the bag, though, and a message appears in red on the screen :
"You can't carry any more of those items"
... But I have no other moonstone in my inventory...
I dropped the item, abandonned the quest, took it back but same story... I checked my character sheet to see if it was an item I could have equipped, but it doesn't seem so... I never did that quest, so I could miss something.
Any idea ?