Dark Nihilism is the philosophical rejection of all values, meaning, and purpose. It's the realization that life is but a meaningless, godless, and uncaring expanse, and that we are all just floating specks of dust in an infinite, uncaring void.
Or, you know, maybe just a bunch of people trying to find meaning and purpose in a cold, uncaring universe, because, you know, that's what humans do. Either way, it's a real downer.