Master of Arena took the Arena set up, which was an optional feature in Project Phantasma and made it integral to the game’s plot. In addition to playing missions to advance the storyline Arena matches were also requisite to advance the plot. Like Project Phantasma before it, Master of Arena allowed players to import save data from previous games and allowed them to carry over parts and credits to help them when starting a new game. Source: Wikipedia, "Armored Core: Master of Arena", available under the CC-BY-SA License.