You can go into a follower dungeon or a delve real quick and use meta, target a party member and use a reflecting prism to swap appearences then a projection prism to copy the appearance back and youll be stuck with it for 30 minutes or until you die, giving you semi “perma” demon form. Quest or dungeon, can keep refreshing it.
Side note, works with any form in the game. Toys that cant be used in combat, things like that. Shaman ascendance. I play my resto druid a lot in perma tree form. Dungeons with water ill turn into a dolphin, copy back and play for a while as a dolphin…Good time. ::