This is where the plot starts to thicken a little. Enjoy.

Chapter 4: The Masters
Ryet came out of his reverie as they started to climb the mountain. Each step they took was a painful reminder of the steps he had taken down the mountain toward Cornelia, which was what had started this whole thing.
They climbed wordlessly for nearly an hour. Everyone focused on their goal ahead of them.
Suddenly, Ryet stopped.
"What is it?" asked Link.
"Nothing." said Ryet. "Go on without me. I want to investigate something I saw in the basin." he said.
"We're almost there. Are you sure?"
"I'm positive." he said before walking back down the path.
Link looked at Axel, who shrugged.
They continued up.
Finally, they reached a sort of palace. A grand entrance welcomed them, but the place was dark, and it seemed empty.
A voice rang forth.
"Do you come with the powers of light or the powers of darkness? Do not lie, for I can sense it."
"We come with light!" said Link.
There was a pause.
"Enter."
They strode into the castle.
They entered a cathedral-sized room, with a round stained-glass window high on the wall. Two thrones stood at the end of the room.
In one of them sat an old man. He had long black hair, steamed with grey, tied in a ponytail. Scars covered his face, but he looked powerful. He had a metal Keyblade sitting beside him, but an ethereal one was in his hands, at the ready.
"Who are you, and what business do you have in the Land of Departure?" he asked in a deep gruff voice.
"I- I am Link. These are my companions Axel, Demyx, Exsan, Sean, Rega, Malon, and Xemyli. We heard that you have much knowledge on the subject of the Keyblade. We seek your guidance."
The man stared at him.
"Who told you I was here?"
"His name is Ryet."
The man's eyes widened a fraction of an inch for the briefest of moments before his face returned to impassiveness.
"Yes, I am well-versed in Keyblade-lore. Do you know where it is you are?" he asked.
"No, sir."
"You stand in the Land of Departure. This was where many pupils once studied how to properly handle the Keyblade. After a certain test was passed, that person may be considered a Master. I myself am a Master. My name is Xehanort. What is it you seek to know?" he asked.
Link looked directly at him.
"Master, one of my greatest friends had his body stolen by one of my greatest enemies."
"What were their names?" asked Xehanort.
"My friend is Rytex and my enemy is Ganondorf."
A peculiar expression crossed Xehanort's face. His eyes widened in unmistakable surprise.
"Rytex! And Ganondorf!" he said.
"Y-yes. Why are you surprised? Do you know them?"
"Know them? Better than that. Do you know who Ganondorf is?"
"He's the wielder of the Triforce of Power, and he wants to rule the world." said Link.
"More than that. Ganondorf is the fusion of one of my pupils and one of my best friends. I taught a boy named Panadorf many years ago. Master Ganon was my friend, but he became steeped in darkness and sought to bring about another Ruin and Creation. So he caused Panadorf's heart to be steeped in darkness before assuming control of it."
Xehanort shook his head sadly.
"Thanks to the efforts of one of my other pupils, Panadorf's memory was erased. The new creation, Ganondorf, has no idea who he is, but apparently, Master Ganon's personality is starting to show. We cannot allow him to gain full control. Can you please relate to me the full details of what has transpired in relation to this event?"
Link nodded and launched into an explanation about everything that had happened since their return to Hyrule, including the part about Bahamut's death.
When he reached that part, Xehanort was completely thunderstruck.
"Bahamut's been killed!" he shouted.
Axel nodded.
"Yeah. Ganon decided to stab him with the Blood Sword."
Now Xehanort was downright horrified.
"The BLOOD SWORD!"
Link knew something was dreadfully wrong now.
"What's so special about it?"
"Do you know why it's called the Blood Sword?" he asked.
"No." said Link, confused.
"That sword has the power to absorb the magical energy of whatever it kills. As long as blood is spilled over it, the wielder gains any power the victim had. And what's more, it was Bahamut who was killed by it. This means Ganon now has the power of Mega Flare."
"Mega Flare?" asked Demyx, slightly confused.
"Mega Flare was Bahamut's most powerful attack. It would launch a blue fireball of such stunning and overwhelming energy that whoever fought it wouldn't stand much chance of surviving. Ganon has started to become much more powerful. However, he told you Rytex had vanished from the Ultimate Darkness?"
"Yeah. He said that Rytex had found a host or something."
Xehanort closed his eyes momentarily.
"What are you-" stared Link, but another voice filled the room.
"Don't question him while he's doing this." said Ryet, stepping into the room.
"Why?" asked Link.
He couldn't help but notice that Ryet looked different than any time Link had seen him.
Ryet was usually cheerful, and a little laid back, even in battles. Now, he was serious, with a powerful gaze focused intently on Eraqus.
"He is trying to find Rytex. Or, more specifically, who Rytex is hiding in." he said.
"How?" asked Axel.
"By looking for me."
"What?"
This caused a lot of confusion.
Ryet sighed.
"I suppose I had better start from the beginning, or rather, the most basic." he said, holding a hand out.
There was a flash of light and a Keyblade appeared, though he held it in a strange way, in a back-hand grip rather than like a normal sword.
Link had semi-expected this, so he wasn't totally surprised by it.
"I have been able to wield one since I was a boy. I took on an apprenticeship to a Master from a young age and I studied under him for four years. The master I studied under was Master Ganon." he said.
Everyone made cries of shock at this.
"Yes. I studied under him. Eventually, there came a point in time where he began to teach me how to balance my heart. However, the darkness in me was beyond my control. He tried to teach me to control it, but then something went wrong."
He coughed briefly, then continued.
"When he discovered how powerful the darkness inside of me was, he told me he was going to remove it from me. So he took his Keyblade and extracted the darkness inside of me, but it was so powerful that it took form. It became a person."
"Rytex." said Xehanort, without opening his eyes.
Ryet nodded.
"So Rytex is the embodiment of the darkness that was inside me. Or I should say, he was. Now, after Master Ganon's mistake, Rytex fled, and I lost my memory for a time. It was then that Master Ganon brought me to Master Xehanort. I was trained under him. Soon, I reached the rank of Keyblade Master with the help and the companionship of Panadorf. We both made the rank of Keyblade Master and we were both given assignments to aid countries that would play an important role in the world's future. I would aid Cornelia, and Panadorf would aid Hyrule. He grew familiar with the boy who would later become the first King of Hyrule, Gustaf. While he was there, he encountered trouble with containing the Darkness inside him, but Master Ganon was able to help him temper it.
Eventually, a rift grew between Master Xehanort and Master Panadorf because of his darkness and Master Xehanort's devotion to light."
A corridor of darkness opened at that very moment.
And out stepped Rytex/Ganondorf.
They all were stunned and pulled out weapons.
Link reached for the Master Sword, but instead drew the Keyblade he had received.
Ganondorf looked delighted by the discovery that he could use the blade.
"Excellent. It seems you may very well serve a purpose in my plans."
He held his hand out and his Keyblade appeared. It was silver, with a relative X-shape to it.
"My plan now is to open the Door to Ultimate Darkness. To do that I need the χ-Blade! I need a soul of light who can wield the Keyblade to do battle with, one that is equal to me in ability. However, you are not powerful enough yet, young Keyblade user." he said to Link.
"What?" asked Ryet. Suddenly he looked a little afraid.
"Yes. Of course I mean you, Master Ryet. Once you find Rytex's soul, you'll be forced to assimilate him, which means I'll be there to fight you once you have regained your light. As I have Rytex's body and his power of darkness, you will absorb his light and we will do battle!"
He laughed for a moment.
"But of course. I must wait for Xehanort to finish scrying Ryet. And I'll handle the explanation now. See, Ryet left out a few details, perhaps not on purpose. And I only just regained my memory, so I can fill in the gaps." said Rytex-Ganondorf with an evil grin.
"Master Ganon!" shouted Ryet.
Rytex's body vanished, replaced by that of an old bald man with a white beard, with a few sparse hairs of red. His edges were blurred and he looked like the Ganondorf spirit that Link had fought, though his appearance was that of Master Ganon's.
"See, after Panadorf and Xehanort squabbled over Xehanort's petty devotion to light and Panadorf's choice to balance himself, a message came to Xehanort. Apparently, I had been kidnapped by someone who left the codename Χ. Panadorf and Ryet came to my aid. Χ turned out to be Rytex, whom I had created while training Ryet. He had been too weak to access his darkness, so I brought it out and gave it form, and it took the name Rytex, adding an X to his name as a reminder that he was created to fuse with Ryet in the future to forge the χ-Blade. He served as my pupil, creating tests for Panadorf."
Ryet was glaring at Master Ganon with fury in his eyes.
"When they arrived at the Badlands to attack me... No. I will just show you."

R&R, as usual.