This is a great series on black holes that I am a fan and I have been trying to keep learning about it. Black hole swarms is a cluster of blackholes that feed of eachother and can take massive amount of energy into them. Sometimes it might look like a large blackhole is really just a cluster of smaller black holes.
That said keep in mind that a single black hole the size of a spec of sand can take a star as large (relatively speaking) as a large lake. So this is really frightening and maybe we can consider these blackholes to take large galaxies or rather large galaxies just being consume by these clusters.
So this swarms could become sort of a galaxy birther. What do you think?