How do you get the fierce deity mask on majoras mask?

Answer 1

Obtain all normal masks. Then, have the giants stop the moon from falling. When on the moon, some...interesting people will take your masks when you play with them. When you don't have any more masks, talk with the guy wearing the majora's mask. No one wants to play with him. When you talk with him, he'll mention how you have no more masks to play with. Then, he gives you the infamous Fierce Deity Mask.