Good or Evil Sory Line
Once you have beaten the White Bishop, the Diva of Twilight will ask you to choose to keep your Wand, or part with it.
If you decide to keep the Wand, you will continue the Evil story line.
If you decide to give up the Wand, you will continue the good story line.
Both have different elements and endings.
New Game with Stats
Once you have completed the game, either through the Good path or the Evil path, you will be asked to save the game.
Save the game. When you load it you will begin the game again, however you will keep all of your current stats, levels, items, etc. The game will be more difficult as the non playable characters have higher stats as well.
Unlock the Bosses for Free Mode
Once you have defeated a boss in the single player game they will become available in free mode.