Moon Clefts are, as the name suggests, Clefts that live on The Moon. These are the most powerful versions of Clefts, and can also be found in some of the later areas of the Pit of 100 Trials. With a very high defense value as well as high attack, these guys are better off avoided.
Super Paper Mario
These enemies reappear in Super Paper Mario as well. They are found throughout Chapter 5, but oddly enough are still named "Moon Clefts," even though they aren't ever on any moons. As another point of interest, regular Clefts don't appear in the game either.