There are six bonus characters you can unlock (not including DLC characters) in Soul Calibur 5 for the PS3 and Xbox 360.
Here are the unlockable bonus characters, and how to unlock them.
Alpha Patroklos – Complete Story mode
Algol – Beat Algol in Arcade mode or Legendary Souls mode
Edge Master – Complete Story mode
Elysium – Complete Story mode
Kilik – Beat Kilik in Arcade mode or Legendary Souls mode
Pyrrha Omega – Complete Story mode
Check out my other article for the complete list of unlockables in Soul Calibur 5.
