Numel stores magma of almost 2,200 degrees Fahrenheit within its body. If it gets wet, the magma cools and hardens. In that event, the Pokémon's body grows heavy and its movements become sluggish.
Numel is extremely dull witted—it doesn't notice being hit. However, it can't stand hunger for even a second. This Pokémon's body is a seething cauldron of boiling magma.