Wallavy

Few monsters in the KonoSuba franchise have an origin as domestic as Wallavy's diet. Wallavy is a self-replicating slime composed of warabi mochi, the jelly-like Japanese confection, taking the form of a yellowish-brown blob with a glowing red core and budding off small clones that lack cores of their own. The creature is an artifact of a past age, judged dangerous enough that it lies divided and sealed inside purpose-built devices hidden in the depths of various dungeons, since a thing that endlessly multiplies edible jelly is also a thing that endlessly multiplies. As it feeds and grows, its shape trends toward its namesake, a wallaby, complete with armor-like metal plates. For most of the world it is nothing but a sealed rumor in the dark.