-( Story related, cannot be missed )-
Valkyrie, Chapter 6: Mercedes
The newly appointed Queen of the Fairies will be your boss, and she won't come alone. Time and again, her legion of elves will fall in line to give you more trouble. You can use them to gather Phozons for more PP, or perhaps they could drop a few potions you could turn around to use. For the boss herself, she is more of a straight-forward shot, so if you deal some damage and then hop over her, you can avoid most of the damage she could deal.