cryptid

noun

1. A creature known only from folklore or legend, the existence of which is not proven by scientific observation.

   “Now comes perhaps the cleverest tag of all: cryptozoology. It refers to the search for new animals, animals dwelling in unexpected places, and most importantly for "X-Files" scriptwriters, "cryptids"—legendary creatures such as the yeti.”

   “Well, that's a painting of the mysterious Brown Blur. It's a cryptid that allegedly roams these very woods.”