Gelatinous cube

The gelatinous cube is a living, amorphous blob of slime in the specific shape of a cube. While soft and malleable, their touch is often acidic, and they can dissolve most materials they come into contact with. Some have numbing or paralyzing effects. They are mostly found in caves or dungeons. They can be particularly dangerous in confined spaces, filling entire corridors, slowly disolving anything caught in its mass.

Source
The g elatinous cube is a creature from the D&D universe.

Media
Gelatinous cubes appear in the following media: