Even deeper, under the realms of mud, there are vast kingdoms of slime, oozing from all the underworld caverns, tunnels, pits and filaments holding this twisted universe together. The goo building this world is clearly alive and lukewarm, blobbing and embracing all living things unlucky enough to end up in the underworld. Masses of gelatinous matter are flowing through the caves, which makes geography extremely difficult, as the whole realm is endlessly transforming and twisting itself into new shapes. Dimensional defects often open portals and ripples in the spacetime, changing local gravity or sucking up whole oceans of goo to be spit out elsewhere, of course with all beings swimming in the green fluids.

Slimeworld is a closed ecosystem, where most of the energy comes from magic influence, radiating everywhere. Slime, being alive, often becomes twisted into weird forms, often resembling mushrooms, plants or weird sponge like structures. All bioplasma cells have collective consciousness, effectively creating an universe-sized living ocean of goo. The mass of slime is always accepting new beings entering it. Those who choose to remain in the warm goo are gently dissolved in the huge gooey stomachs and join the collective consciousness, losing themselves in a warm, dreamlike state of being.

Slimeworld also houses errors of its bioocean structures - some cells of slime become renegade and merge into beings of their own. Free of the collective will of the slime, they take the form of blob monsters, crawling the underworld and eating all kinds of prey, trapping them in their own digestive systems and abusing their dissolved matter. Goo monsters tend to have a powerful lust for tickling humans and swallowing laughing people, often crawling up the slime pits to populate the world of Sewers and sometimes even the Jungle and Earth.

Magicians using the power of the Slimeworld are called Slimemancers: they are often lustful and greedy, using their skills to suck their victims into the living slime and keeping them captive in their arcane lairs.