A space between worlds would imply nothing existed there. Anything that came from there, if existing in nothing was possible, would be even more bizarrely surreal than MC and Light. See my above post for my thoughts on other dimensions. MC and Light's personalities and powers don't really fit with supposedly coming from a realm of nothing. They'd be much better off coming from somewhere else. Also because void energy is a bit too handwavey. 

Ibs lifted is preferable. And for Light she shouldn't be that superhumanly strong, maybe between 500 and a thousand pounds.