The Lunar Virus, also known as the MoonCell or Luna Virus, is an enemy from Final Fantasy IV. It is not a particularly threatening enemy, and will run away after some time. It is best to hit it with powerful attacks such as Bahamut or Leviathan to bring it down before it escapes. It is usually accompanied by Prokaryotes and Eukaryotes.
Luna means "moon" in Latin, Italian, Romanian, Russian, and Spanish.