From alchemist to assassin, from ninja to samurai. We only need 3 things to unlock extra classes: 1. Class Point (CP)- 500 to 1000 CP per class. 2. Co-op achievement- Each class needs a special title to unlock. Eventually, you have to unlock all the classes, so just go ahead and clear all the EX stages. Once and for all. 3. Warrior or Mage Creed- You can get these items at EX stages, particularly EX 1-3 and EX 3-1.