Riku finds himself sitting alone on the beach back at his home island. It seems he missed his home more than he thought he would. As he is remembering a time when he used to have contempt for his home, he notices a few old friends down the coastline. Riku sprints toward Titus, Wakka, and Selphie with an excitement he has not felt in a long time. Something is wrong and the three not only do not respond, but disappear as well. Riku is then given the Key of Beginnings Card.
Once Riku becomes playable, look at the map to see the direction of the crown door. It appears to be in the west side of the map, so make your way there as best as you can.
Once you approach the door, make sure you are fully prepared, then use the Key of Beginnings to proceed.
During the scene, Kairi appears before Riku only to quickly disappear. Zexion speaks from behind Riku and explains that all that is left in his heart is darkness and bad memories, which is why he is only met with despair here. Riku explains that he remembers all of his friends and that he is fighting for them, although he seems to forget a very important detail that Zexion cannot wait to remind him of. It seems Riku destroyed this place in his rage. Riku, in his anger, destroyed the islands and let the darkness in, and now he belongs to the dark that he wrought. Riku is the bringer of destruction—the being Sora fought before. Riku is Darkside.
Boss Battle: Darkside
After you pick up the pieces from your mind being blown, begin this battle confidently. Darkside is still just as easy as before, and this time you are Riku. Darkside has the same moves as before, but Riku’s attacks do much more damage than Sora’s did. Darkside begins by punching through the ground, creating a void that brings forth Heartless that can be dispatched easily. This move leaves him wide open for three-hit combos that can take him down a full life bar if you are quick enough.
Easily break Darkside’s moves to enter D Mode and use Sleights as often as you can.
Darkside sends a barrage of his own in the form of dark balls that fall from the sky. Roll around to dodge them as best as you can, which should keep you from getting hit. Continue to enter D Mode and use the strongest Sleights in your arsenal to bring this guy down. After the fight, you level up and gain the Darkside Card.
Following the fight, Riku notices Sora standing alone. Run up to him and speak with him. Sora is apparently not as happy to see you, and he attacks Riku without question. Riku asks why Sora is fighting him, but before answering, Sora blasts Riku with a light beam from his Keyblade. Sora says that Riku is just a pawn of the darkness, and then blinds him with a blast of light.
Riku awakens, engulfed in light, and standing in front of Kairi. Kairi explains that he does not have to be darkness anymore, and that his true strength is when he is in between light and darkness. Kairi informs Riku that both the light and the dark will make him stronger, and for him to stay in the twilight in between. As the conversation goes on, it seems Naminé is speaking as Kairi, however it doesn’t matter, and Riku is renewed with purpose and strength—his dark strength.
Riku awakens in his dark form and slices through Sora to uncover that Zexion was taking the form of Sora the whole time. Zexion is baffled and cannot understand how Riku has become so strong. This triggers the final battle with a member of the Organization.
Boss Battle: Zexion
Zexion might have been a challenge if Riku was not able to fully control his dark powers, but alas, he can. Riku is permanently in D Mode now, giving you free reign to use dark Sleights to pulverize Zexion freely. Zexion begins the futile fight by using a move called Cyclone Snatch that is easily avoided.
Zexion also uses a move called Dark Punisher where he grabs you from behind and holds you to drain your energy. There is not much you can do here but mash buttons in hopes that he will let you go.
After a little while, Zexion splits into several forms of himself that all simultaneously attack you. It may seem difficult at first to decipher which one is the real Zexion, but watch his patterns and placement to pick him out of the fray.
Another annoying move is called Catastrophe, in which all of Zexion’s forms shoot an energy blast that connects in the middle, and then the Zexion duplicates spin around in a circle covering the entire area.
Once you get Zexion’s pattern down, he can be very simple. Just pick out the right Zexion by remembering his patterns and lay in with Sleights of your own. In no time he will be beaten and you will have the Zexion Card in your clutches.
Zexion is amazed at how far Riku has come in such a short time. Zexion gasps that Riku has always been afraid of the dark that hides inside him until now. Riku denies that he feels the same, and briefly comments that he can control his darkness that resides in his heart, and runs Zexion through with his blade. Zexion disappears in shame.
Zexion reappears back in Castle Oblivion, but he is not alone. Axel and Riku Replica are with him. Zexion attempts to use Riku Replica for his own purposes, however it seems that Axel has already gotten to him first. Riku Replica has another idea in mind, and it does not involve Zexion remaining upright.
The next scene shows the real Riku back in the castle. Instead of a warm welcome, Ansem immediately controls him like a puppet. Even with Riku’s newfound abilities, it has only made it easier for him to be controlled. Just as before, Mickey appears to save him from an unfortunate fate. Mickey came from the darkness by the help of the last card in their possession. Now that Mickey is there in the flesh, it is time for the two of them to move on to the last destination. Save your game and use the last card to enter Twilight Town.