Unlocking Good or Evil Story Paths: When you have beat the White Bishop you will be given a choice by the Diva of Twilight. You can either choose to keep your wand and branch off into the Evil storyline or you can decide to give up your wand and branch off into the Good storyline. Both storylines have different endings.
Unlock New Game with Bonuses: Beat the game with a good or bad ending and you will be prompted to save. Save your file and then when you load you will start back at the beginning of the story but you will have kept ALL your stats, levels, and items. The enemy NPC's will have also increased in difficulty.
Unlock Bosses to use in Free Mode: When you defeat a boss in Single Player mode you will be able to use them in Free mode. The only difference between the bosses other than appearence are the types of monsters you can choose to have in your party.