Now, I never knew this was so easy. All you have to do is run away from Frostwind in the first part of the boss (It would help if you were in 1 piece) and Frostwind brings you to an arena. When Frostwind comes up shoot him and then ground-pounce on his head 4 times. Also, above you there is a girl in a cage and she gives you power-ups. You save the girl when you beat Frostwind.