Dark Prince Mask
The Dark Prince Mask is the mask worn by Masked Satan at the end of Puyo Puyo TSU. It is plated with gold. However the legitimacy of this gold is questionable, since the mask only last one game of Puyo. Other than the gold plating, it looks like a typical Oprea Mask. In english languages, it is the Dark Prince Mask and not the Masked Satan Mask because in Minna, Satan had his name changed to Dark Prince. Furthermore, at the time of Minna's release, America had yet to be exposed to Puyo Puyo TSU.
In Minna de Puyo Puyo, after defeating Satan in the final course, before the credits roll, Carbuncle eats the mask. Arle takes out the mask, and it unlocks Satan to use in Double and Everybody Puyo Pops.