The wearer's mouth and eyes will become invisible, their skin will turn gray, and their face will be heavily shaded. If you look close, you can still see your nose though (as well as any Face items equipped)!
When equipped you receive this message in game: "You've got quite a pokerface. (Mark of Growganoth mod added)"
When removed you receive this message in game: "Your face is back! (Mark of Growganoth mod removed)
