Defeat 2,000 monsters to unlock both Galaxy Mode and Universe Mode (the latter is the most difficult).

To unlock the secret dungeon, the Cave of Trials, head to the save point just before you fight Gabriel. Your save icon will be blue. Now, head to Fun City and go to the north side of the Arena. Here, you'll find an old man that says he can recover your memories. Accept, and you'll be transported to Arlia on Expel. Leave Arlia and travel to the Cave of Trials, located in the southwest corner of the world map. It's a dot on a desert island.

Beat the game to unlock the Voice Player. Each additional character you beat the game with adds their voice for sample playback.

In Kurik you must witness the Private Action of Philia telling people to evacuate. After reaching the final save point in Phynal, leave Phynal and viewa Private Action in Centropolis. Philia appears here in the main building's lobby. Talk to her this time and Gabriel's limiter will be removed and he will be ultra-powerful. Make sure your levels are significantly high before taking him on.