Source: #225

For now, this only applies to one item, but it may come in handy in future patches. We can probably use this API: https://www.townlong-yak.com/framexml/live/Blizzard_APIDocumentation#C_Covenants.GetCovenantData

Also, a standardized way to display this limitation would be useful:

• When adding a waypoint for items restricted to a specific covenant, there should be a suffix similarly to the Warfront rares that are limited to just one faction to make sure no one is confused
• The mouseover tooltip should likely display something along the lines of "Covenant: X" in the tooltip, but only if looting the item is actually impossible for the player's covenant (in red, similar to the "Already Known" text perhaps)
• TBD: Possibly removing the tooltip entirely if the "filter unobtainable items" checkbox is selected might make sense? I'd have to test it ingame to see if it makes sense

It doesn't seem worth adding these optional features, so merely hiding the tooltip and preventing attempts must suffice. This is included as of 7b8128c.