Halloween // Ideas for a creepy halloween costume?

Want a truly disturbing, non-human monster costume for Halloween, something that looks completely wrong and terrifying.

A couple ideas I had: a four-legged/quadruped horror creature, or one with a mechanical jaw/mouth that opens when I speak (or simple trigger). But I have no clue how to build either.

Pure nightmare fuel, inhuman proportions, eldritch/alien vibes only.

Any creepy concepts or similar builds you've seen or done?

(I don't have a ton of money, if it doesnt cost extreme prices then good.)

Thanks!