Unlock Hidden Characters:
Highlight the "Set Teams" option on the "Mayhem" mode selection screen and press Circle +
Square, Select(4), Start(3), Square(2), Circle, Circle + Square.

Beta Razor:
Beat the game on the hard difficulty level with the Teknos, then you can select Beta Razor under
Mayhem Mode.

Show One Player Strategy Maps:
Highlight the "Set War" option on the "Strategy" mode selection screen and press Circle + Square,
Select(4), Start(3), Square(2), Circle, Circle + Square. 

Super-Prana Devil:
To get Super-Prana Devil beat the game on the hard difficulty level with the Arcanes.

Extra Maps:
Beat the game on the normal difficulty level as the Arcanes to get The Maze. Beat the game on the
normal difficulty level as the Teknos to get the Menhir Circle.

Unlock Hidden Battlefields:
Highlight the "Accept Teams" option on the "Mayhem" mode selection screen and press Circle +
Square, Select(4), Start(3), Square(2), Circle, Circle + Square.