Wherever there is a galaxy there is a BH at its center, then there are all the smaller ones from massive enough stars that collapsed and exploded in a super nova creating a BH. Stars not large enough will become white dwarfs or when larger a neutron star. A dead star on rare occasions become a magnatar that is almost as dense as a neutron star but s a magnet so strong it will pull the iron out of your red blood cells a parsec away.

Black holes with their gargantuan gravity are in turn surrounded by heavy non interactive dark matter gravity that string together in what looks like filaments of a sponge from a distance of about a quarter the diameter of the universe. Google filaments of the galaxy to what the universe looks like if you had eyes the size of the solar system.

It seems like the recent discovery of our BH creating neutrinos is probably what is left after the black hole reduces everything down as far as stuff can be crushed.