April 4, 201213 yr The Final Mix ones I think are Secret Bosses (Armour of the Master and No Heart), but I think the regular ones aren't secret, just optional.
April 4, 201213 yr Mirage Arena is a optional world where you fight, you guessed it, optional bosses. Thread RULED by Uncle Dolan.
April 4, 201213 yr Secret boss practically explains itself. Mirage Arena Bosses would be Extra bosses
I think they would be optional boss which is the same thing so I think so