The Acumen Mask for the Wizard class.
I have conferred with several wizards across the level ranges. Thus far in the Estate of Unrest a Greater Darkbone has yet to drop a Darkbone Skull. I personally have cleared the basement repeatedly for nearly 24 hours and I have lost count of how many I have killed. No skull obviously.
Gintu a bard told me he is certain he has seen a skull drop, yet no wizard has. I am simply asking to know for certain whether or not the item is in game and dropping. I remember on live it was a longer camp than other parts of the quest, but not this long.