could be an Org only spell, somethin they discovered or created that mickey learned during his undercover time
yep and that would be a connection right? although i find it weird that xaldin woudn't notice a mouse in a black coat. sora and friends spotted him immeadietly if im not mistaken.
personally i don't think he used the coat to go undercover, rather to not be bluntly obvious to his enemies that theres a king walking down the street. but that's just my opinion.