You realize that Bill got the power to do so through some kind of unstable rip in space-time that threatens all of existence right? I don't know where it goes, but it looks kind of like the... Nah couldn't possibly be the Time War that's spilling out into Gravity Falls... By the way, do you know a being who's name should never be spoken, big, purple, kind of resembles a moldy loaf of bread with Gorilla arms...?
That looks more like a purple gumdrop man... and it has a face... The thing I was talking about has no face.
You didn't say faceless. You need to be more specific! Specificity is good; for example, how many shadows do you have? That's a specific question that requires a specific answer.
Found an image... For reference it's the big purple guy on the right, next to the pink demon girl?(Assuming girl because it looks like a humanoid female, but you never know with creatures from other dimensions...)
'The Professor' is dressed as the 4th Doctor, and not only did he wear that delightful hat and colourful scarf, he also had a thing for jelly babies