Mind Flayer Skull

D&D 2014 item: Mind Flayer Skull. Source: Waterdeep: Dungeon of the Mad Mage. type Other, Unknown (magic) rarity While you have the skull in your possession, you are invisible to mind flayers, as is anything you are wearing or carrying. Other Unknown (magic)

Source: Waterdeep: Dungeon of the Mad Mage, p. 197 - Licenses and attribution