Amorphous creature

This is a List of fictional alien lifeforms from science fiction by physical features or form.

The amorphous creature is a common trope in science fiction. Usually it is depicted as a living mass of jelly, slime or liquid-like substance that can take any shape it wants.
Amorphous creatures are to be distinguished from shape-shifters that can change their appearance due to their body material to mimic a living or non-living thing however they like.
Metaphorically, "amorphous" refers to any structure, body, figure, text or speech that lacks a distinct form or order. In Japan most amorphous creatures (especially those made of liquids) are called Slimes.

These fictional creatures purport to thrive in the biome of outer space.

Shape-shifters can change their appearance due to their body material to mimic a living or non-living thing.

...
Wikipedia