Theory: Dimentio and the Magiblots

Abstract
Dimentio and the Magiblots are originally from the dimension where Castle Bleck is located.

Arguments

 * Argument 1: Dimentio shares many similarities with the Magiblots. They’re all magicians and their main attacks involve summoning spells themed after themselves. Magiblots can also teleport, flip and move between dimensions as Dimentio can. They also share many physical attributes, having black bodies with white outlines, disembodied hands that they use to perform their magic and square baubles on points at the ends of their heads.


 * Argument 2: Castle Bleck and the dimension surrounding it are comprised of black material with white outlines, much like Dimentio and the Magiblots. Blue Magiblots, Yellow Magiblots and Red Magiblots are the only completely unique enemies found in this dimension, and they aren’t found anywhere else throughout the main game, implying a stronger connection between them.


 * Argument 3: According to Carson, Dimentio approached and befriended the count all on his own. The count even turned him away once, until he read in the Dark Prognosticus about the role of someone similar. If Dimentio is from the dimension Castle Bleck is located in, this would’ve given him the perfect opportunity to approach the count.