Literally a mobile, sentient, self-cleaning organic toilet, this rarely-seen monster is considered a luxury by some, unnecessary and tasteless by others. Difficult to identify as a monster when withdrawn into its shell, it passively consumes all manner of waste and garbage, storing its own highly corrosive waste product in its tank until it finds a suitable place to expel it - sometimes as a weapon. Besides their popularity as novelty appliances, gag gifts and cruel practical jokes, they are occasionally seen as multi-purpose security guards, custodians and emergency facilities at outdoor events.
A toilet monster was a long time coming. I even sketched one way back when I was first drawing "necromon," but it was a sort of floating nautilus-like creature. That might still be really cool, but I think one is enough and I like the idea of it being more of a polyp, anemone or crinoid sort of form.