Almost as powerful as Mythic, but flawed and limited. Yet, more common to find that a Mythic item.
Traits and rules about Ethreal:
* Powerful stats and attributes, close to, but not accurate like a Mythic.
* Low durability (only items with durabilities).
* Can't be repaired.
* Always class based.
* Useful during bursts, or for a limited continuance time.
* Can be traded with NPC to get materials for future crafting. Broken means less materials.
* Account-bound at drop / on pick-up.
* Unique item that is fairly rare, but more common than Mythic.
* Once picked up, also added as a transmog (or whatever they call the system to change its appearance)
* Needs two images for each item, one whole, one broken.
* Once broken, it looses all the visual effects and just deals minimal requirment of damage (1-2) or protection, what ever suits the actual item.
* Once broken, you still use the item, but you hear and see that something is off. Perhaps a timer of some kind can be shown to prepare you to actual change item.
* Could almost be called a 'Mythic teaser'.
If Mythic items have a Purple beams, Legendaries orange and Set items green, this once could have a grey/purple feel to it. when it shows on screen. I think a normal star on mini map is fine no matter of tier in set/legendary+ items.