Box Slimes are, as their name suggests, box-shaped Slimes and are of a reddish hue. This box-like form supposedly results from a Slime being stuck in a box for a long period of time. Despite this distinct shape, they are still as gelatinous and stretchy as their normal Slime counterparts. When breeding, any given Slime as the pedigree with a Material monster will typically result with the egg of a Box Slime.
Monster series appearances
box gives this
slime it's shape
Box Slimes can be encountered in the Medal Man's Gate where they will either attack with Blazemore or Ramming or support fellow monsters with Upper. Typically, any Slime pedigree with a Material mate will create a Box Slime. They are useful when bred with a Material pedigree since the result will usually be a Mimic.