-form nebulae & form white dwarfs. White dwarfs have a 1/3 of the mass of their former self. The output a similar amount of energy. Eventually, they will burn out as well, this causes it to form a black dwarf. When the universe goes dark, these may form Ionic Spheres due to an assortment of things.
An alternate path is the gravity becomes so out of whack that a war is started. The star vs it´s own gravity. If the star wins, a Neutron star is formed. If gravity wins, a black hole is formed.