This feature is one of the most time consuming events in Baten Kaitos Origins and requires a complete Magnus Gathering (going through five different stages which means five different Quest Magnus). The earlier you get the Heartflask side quest the easier it is to complete. The Heartflask side quest is given to you by Georg who is found in the Nihal desert when you have a 'Baten Kaitos: Eternal Wings And The Lost Ocean' game save on your GameCube Memory Card.
When you have defeated the final boss view the credits and remaining scenes and you will be given the option to 'Save'. 'Save' and you will be returned to the 'Title' screen. Select 'Load Game' and load your 'Save' file and you will begin a new game with your group intact.
To be able to rank up in the coliseum after rank 1 you must first complete ALL the matches in your current rank and have accumulate enough RP. Complete the following quests to unlock the corresponding rank.
Unlock Rank 1: Reach Alfard a 2nd time and get the Dog Tags
Unlock Rank 2: Read the letter in the shop in Sheliak (Diadem)
Unlock Rank 3: Read the letter in the shop in Cebelrai (Sadal Suud)
Unlock Rank 4: Read the letter in the shop in Komo Mai (Anuenue)
Unlock Rank 5: Read the letter in the shop in Vega
Unlock Rank 5 - Qualifier: Received after Rank 5 has been completed
Unlock Champion: Complete the Champion Battle
Unlock Champion - Advanced: Complete the quest in the champ's room and then complete ALL advanced battles.