I think the concept of Hadar; a sentient evil dying star, is really cool. I want to use it as a BBEG for the very end of a campaign, with other characters like cultists, neogi, vampires and more being the lower level threats. What sort of force would be able to destroy something like Hadar? Can it be killed? Would the way to go about it be to deprive it of things to consume? Who or what would be powerful enough to stop it?