MU Online was created in December 2001 by the Korean gaming company Webzen Inc. Like most MMORPGs, players create a character among nine different classes and set foot on the MU Continent. To gain experience and thus level up, a player needs to fight monsters (mobs). MU is populated by a large variety of monsters, from simple ones like goblins and golems, to more challenging ones such as the Gorgon, Kundun or Selupan. Each monster type is unique, has different spawn points, and drops different items. Outside of a duel, PvP fighting is possible but discouraged. When one player attacks another, a self-defense system is activated, in which the attacked player may kill the aggressor within a time limit. Self-defense is also activated when a player attacks an Elf's summoned creature. Outlaws have disadvantages during gameplay, depending on their Outlaw level.[citation needed]