Just when you think that game can't get any creepier.

I know the Fierce Diety's Mask was originally supposed to be an "Adult Link" mask where you'd turn into Link's older form from Ocarina of Time, but they scrapped the original idea because, since young Link can now use all items no problem, turning into the adult form seemed pointless. Instead they changed it to a "100% completion bonus" mask that's OP against bosses, and required in order to see the epilogue credits in their entirety.