Following codes by Jan Wargalla

Fight as Bimorphia
Press Right(3), Down, Square when "Press Start" 
appears at the opening screen. A sound will 
confirm correct code entry. 

Fight as Juni
Press Up, Left, Left, Up, Square when "Press Start" 
appears at the opening screen. A sound will confirm 
correct code entry. 

Fight as Kahn
Press Up(2), Down(2), Triangle when "Press Start" 
appears at the opening screen. A sound will confirm 
correct code entry. 

Fight as Moloch
Press Up, Right, Down, Left, Square when "Press Start" 
appears at the opening  screen. A sound will confirm 
correct code entry. 

Fight as Mongwan
Press Down(3), Up, Triangle when "Press Start" 
appears at the opening screen. A sound will confirm 
correct code entry. 

Fight as Redemptor
Press Up, Down, Left, Right, Circle when "Press Start" 
appears at the opening screen. A sound will confirm 
correct code entry. 

Fight as Stygian
Press Left, Right, Left, Right, Triangle when 
"Press Start" appears at the opening screen. A sound 
will confirm correct code entry. 

Fight as Vodu
Press Left(3), Up, Circle when "Press Start" appears 
at the opening screen. A sound will confirm correct 
code entry.