Quadatrum personally in my understanding is a world where all things and ideas that could not appear in the main world converge. (Where all the main action takes place)
Which makes it a parallel world by the standards of the world we know in the multiverse, but also distinguishes it from other worlds and makes it unique even among them.
Regarding the nature of Yozora and the Nameless Star, if Quadatrum is really a world in which all ideas that have not received a material shell in the world known to us are received in this, then Yozora can indeed be associated with at least Riku and possibly Sora. What if he's the failed nobody Sora and Riku? Regarding Riku, his body was taken over by Ansem and a little more and Riku could have had his own nobody, but it didn't appear since Riku didn't formally l his heart, so his is nothing more than an idea that got corporeality in Quadatrum nobody.
Regarding the origin of the Quadatrum, it is possible that it is a product of the creation of the Masters of Masters or the Book of Prophecy. For as far as I know (If I'm not mistaken) Dandelions also fled to the reality created with the help of the Book of Prophecy.
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In addition, if Quadatrum is a kind of unreality, what should you call the locals? "Non-existent", "Unreal"?
They might be a subspecies of nobody.
In this case, Yozora is "non-existent", "unreal" Sora.
Quadatrum personally in my understanding is a world where all things and ideas that could not appear in the main world converge. (Where all the main action takes place)
Which makes it a parallel world by the standards of the world we know in the multiverse, but also distinguishes it from other worlds and makes it unique even among them.
Regarding the nature of Yozora and the Nameless Star, if Quadatrum is really a world in which all ideas that have not received a material shell in the world known to us are received in this, then Yozora can indeed be associated with at least Riku and possibly Sora. What if he's the failed nobody Sora and Riku? Regarding Riku, his body was taken over by Ansem and a little more and Riku could have had his own nobody, but it didn't appear since Riku didn't formally l his heart, so his is nothing more than an idea that got corporeality in Quadatrum nobody.
Regarding the origin of the Quadatrum, it is possible that it is a product of the creation of the Masters of Masters or the Book of Prophecy. For as far as I know (If I'm not mistaken) Dandelions also fled to the reality created with the help of the Book of Prophecy.
***
In addition, if Quadatrum is a kind of unreality, what should you call the locals? "Non-existent", "Unreal"?
They might be a subspecies of nobody.
In this case, Yozora is "non-existent", "unreal" Sora.