I've seen Fantastic Beasts and Where to Find Them but I can't recall if I assumed that Grindelwald had been using Polyjuice in order to take on Graves' appearance, a la Barty Crouch and Mad Eye Moody appearance, or if this was factually confirmed in the movie. Do we know it was definitely Polyjuice?
I want to know if Graves' could appear in the sequel so is he alive in order for the Polyjuice production to continue or is he likely murdered.