There is a secret door where the merman pit is. It's easy to find. All you have to do is go through the tunnel 1 time as a bat and 1 time as a wolf. At the bottom, there should be an open door at the bottom left in the room.
Submitted by mad man
Castlevania Symphony of the Night - Xbox Live Arcade Unlockables
Apprentice (5) - Defeat 10 consecutive enemies using only magic without getting hit.
Rampage (5) - Defeat 10 consecutive enemies using the standard weapons without getting hit.
Bloodlines (10) - Defeat Dracula in the Bloodlines stage without getting hit.
Changeling (10) - Obtain the Bat, Wolf and Mist transformations.
Demon Slayer (10) - Defeat Gaibon and Slorga.
Weapon Master (10) - Defeat 10 consecutive enemies using special weapons without getting hit.
Familiar (10) - Collect all five familiars in the game.
Warlock (15) - Unlock and Cast all eight of Alucard's spells.
Topsy Turvy (20) - Unlock the Inverted Castle.
Money Bags (25) - Collect a bank of $100,000.
Seeker (35) - Explore 200.6% of the game.
Belmont's Revenge (45) - Finish the game, including the inverted castle, as Richter.
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