The purpose of Arc Arena is simply to have some fun with the monsters and characters of Arc I and Arc II. Arc Arena allows you to use the monsters ravished by Leiza in Arc II for combat against other monsters in tournaments and against other players.
Arc Arena has several different modes for monster combat, Battle Mode, VS Mode, and Tournament. In Battle Mode 3 teams of 4 monsters from each player are pitted against each other. The opponent is of course in this mode the computer and its monsters are made up from a team selection available to it. Your teams will be made up from the monsters in your collection and you must pick carefully to create a balance. At the beginning of a battle you have the option of how you want your monsters to act which can be Auto, Offense, Defense, Avoid, or Brute Force. This pattern your monsters will follow in combat whether they strictly stick to attack, defend themselves, run away like cowards, or in auto do whatever they please. This is the major downfall of this mode, you as the player have no interaction with your monsters, they will move, attack, etc on their own. As mentioned previously you sit and watch as they battle it out. The idea behind this mode is two have at least 2 of your 3 teams beat the other team and you then win a prize and a new monster. Winning against a team of 3 groups allows you to face the next team of 3 groups with a total of 15 groups vailable to play against. Each team has stronger monsters and higher levels with better items and monsters available if you win.