Planet Nine: does it exist?

[GrieferLord]

It could be either or, or alternatively it could be the shattered remains of a destroyed planet on the outer rim. which would be equally interesting.

Could well be - although then, the obvious question would be "What destroyed it?". There's not much that lurks out there - that we know of, at least! 

True, though like all things it could have been natural, the core could have collapsed and or a massive stellar impact. alternatively an alien race could have used it as a testing ground or what have you. either way its just an alternate theory.