I'm not too flash on Physics. Especially not as good as Sili. But here's my knowledge on Black Holes & how they can be linked to the Great Devoid.
When we watched the Great Devoid explode after Drunked Ghol (it was him wasn't it?) tossed Balor's head into it. When I saw this I thought of a singularity (they're great devoids aren't they, in a way) exploding once they're overloaded.
Forrest put forward a much better idea, that the explosion is that Jets which are sometimes seen flowing out of Black Holes, cos this is sure what it looked like.
As far as my understanding goes, when matter flows into a Black hole it can sometimes be split apart (ask Silicon for an explaination of this) and the positively charged particle is flung out with force. And when alot of particles are flung out (ie. when a primordial black hole is feeding on enough matter in the centre of a galexy).
So what does this mean? Well the Great Devoid was created with the destruction of the Callieach, and Black Holes are created with the destruction of Stars.
Does this mean anything? Probably not, but I do like a good ramble.
Maybe you could look at it this way: Many stars had to die before the elements required for life could be made. Maybe the death of the Callieach means something for other life.
Or maybe I've taken it too far.
Ah well. =)