[quote=@mattmanganon]
[@King Kindred] So, have the Heartless got a definitive backstory that the people of the wider universe might be aware of, or are they just seen as general spooky shadow-demons?
[/quote]

The backstory of the Heartless remain unchanged. So there are some legends about their origins, but most people wouldn't know about them unless they've experienced them, researched them, or were taught about them by someone else.