Let's not forget that Beast traveled to a different world through the sheer power of being pissed off
As BS as that is (seriously, the Beast travels through worlds with no protection and he's fine, but Xehanort does it and that's what essentially started the Armageddon?), I always liked how they tied that into the Organization wanting to recruit him.
I gotta imagine a guy who can follow his beloved one from one world to another through sheer force of will would make one heck of a Nobody.