--BOSS BATTLE: DARK PRINCE
The Dark Prince does not attack (he is part of you, remember?). Attack
him with the sword until you enter the Prince's mind.
As the conversation rages on, the Prince must jump from platform to
platform and attack the helpless Dark Prince. If you miss a jump, you
won't die, so don't worry about making a mistake.
Keep making your way to him and attacking him until Farah shows up.
Once Farah shows up, follow what she says and walk up the stairs to the
light. Now enjoy the REAL ending. You deserve it, Mon Congrats!