Contemelias were a neutral 5th-dimensional race that traveled across the multiverse using the Anihilargenesistoriathimiorgost (Anihilaarg for short) to create universes as experiments. The same tool can also destroy a universe. At some point in time the Contemelia died off, but at least one of their vessels still flew across the multiverse labyrinth, as it passed into legends along with its tool/weapon.
Over time, many species started to predict the Contemelia as inter-dimensional beings who played practical jokes on the inhabitants of the universes they'd visit. If the Contemelia did not like a particular universe, they would use the Anihilaarg to reduce it to nothingness.
Due to their body structure being 5th-dimensional, their true forms cannot be perceived by three-dimensional beings. Most three-dimensional beings would instead see a Contemelia as an animate projection of what holds the most emotional sway over them, while a genetometaphomorphic lifeform such as a Slimebiote would instead just see a Contemelia as a mass of energy.