Quote Originally Posted by Rockphed View Post
Getting sufficient density of light is ridiculously hard, and light is probably the easiest of the fundamental force carriers to control. Gravity is significantly harder and we do not currently have any means to direct it...
Since gravity waves travel through spacetime itself, I'm sure that there's some way to assemble galaxies such that gravity waves from multiple sources all get lensed and focused at a single point. (Which might require some elements of some paths to require exotic matter, at which point our best hope of acquiring that is through magic.)

Which does get back to the question of why a society able to manipulate entire galaxies and to cause other black holes to collide at exactly the right places and exactly the right times would bother to do that, since as you mentioned it'd be much easier to just make a black hole by cramming together a bunch of mass and/or light where you want in the first place.