UB-01 is a transluscent creature, whose body is made out of a glass-like substance. Although it is shown to look somewhat like a jellyfish, it constantly changes shapes, and never settles on one.
While evidence of something like a survival instinct can be observed in UB-01, no one knows whether it has a will of its own or any emotions. It’s said that, for some reason, its movements resemble those of a young girl.
UB-01 is a combination of UB, an acronym for Ultra Beast, and 01.