Quote Originally Posted by SeeDRankLou
If I'm wrong, then it's likely that when Ansem's machine blew up, and Riku was finally removed from the darkness, that his weapon may have become a keyblade, since he was finally worthy of one again.

What the keyblade is exactly has never really been explained. Xigbar however did mention that there have been those before Sora, so it's possible the there is a keyblade for every keyblade wielder, and if that's the case then there have been quite a few. Otherwise, one can only speculate.
That's the assumption that I was working under, that Riku had earned his right back to have a Keyblade (not that he did a whole lot). I do think that Riku was supposed to have the Keyblade all along, but any interpretation is available, since the Keyblade never talks. Even Mickey's knowledge of the Keyblade is mostly supported by Ansem's research into the old legends, not from the fact that he uses it. I also use most of Xigbar's explanation for the Keyblade being available to all those who fight a Heartless.

However, it is still unexplained why Roxas can wield two. Sora obviously has the ability to do so, since Roxas has to siphon some of Sora's power to be a Nobody, Even in Valor, Master, and Final, Sora can use two.

In the Valor Form, it says that Sora can use the abilities of both Keyblades, but neither one of them do full damage, when fighting an enemy. Sora is just alot faster. It could be that in order to wield two, you must split the essence into two distinct parts, each giving half power, but the ability to wield two, which is even more dangerous, considering how untapped of the power of the Keyblade remains; this could mean an almost unlimited power, being split. Too bad Sora can't use Magic.

In Master form, Sora does not hold one of them. It could be possible, that the true ability of the Keyblade, is to cast Magic on its own, using the ability of the Master's mind, as well as being swung simultaneously to cause full damage.

Final Form, Sora holds neither of them, and I often find that they often cast Cure Magic/Reflega Magic when necessary, without draining my MP. It also does insaneo damage and combos. But this means that there are two, both having their full powers. This remains unexplained, and I wonder why it can be done.

It could be, since that if everyone who has ever fought a Heartless gets a Keyblade, that Roxas gets one, because he fights Heartless while he is still a part of Sora. When joined back together, that means two essences fighting a Heartless. That could equal why Sora can use two in Final Form, which is essentially Sora being helped out by Roxas, and therefore, being complete.