Player one: Press Circle.
Player two: Press Triangle.
Player three: Press L1.
Player four: Press R1.
Player five: Press L2. (Fate and Sophia only)
Player six: Press R2. (Fate and Sophia only)

Final Secret Boss - Frei/Freya  -  After you beat Iseria Queen at Floor 211 of Sphere 211, you will obtain a Key Item. Now head to Crosel's room and use the Key Item at where Crosel rests. You will end up fighting Frei/Freya.

Getting Adlai And Mirage  -  To get Adlai, after Amina and Dion meet again, head to the Audience Room in Sealand and head out. An event will take place, you will be able to let him join after the event. As for Mirage, she will join you automatically at the Diplo.

*These two characters are playable in Director's Cut only*

Sir Felious' Underwater Garden And VS Mode  -  When your party decides to head to Sealand. You will come to the Iris Plain. Head to the west part of the Iris Plain and you will now see an entrance to the Underwater Garden and a save point. Go through the place and beat the boss to obtain Paracelsus' Round Table. After the war, give the Paracelsus' Round Table to Welch in the Craftsman Guild at Peterny and you will be able to play VS Mode. At first, you only have 6 characters and their 1P and 2P. To unlock others characters and outfits, you need to collect Trapping Cards.

Sphere 211  -  After you beat Gabrielle Celesta at Floor 8 of the Trial Cave, head to Sphere 211. You can now go up to Floor 211.

Trial Cave  -  After you clear the game, head back to Cirlsour and enter the Trial Cave from the entrance at southwest.

Urza Stone Temple  -  After you clear the game, head back to Crosel's room. Enter the area at northeast. You should now see a path to Urza Stone Temple.