Cosmic horror is not the fear of a monster or a ghost but the fear born of a single fact: the universe is utterly indifferent to human beings. Our morality, reason, and survival mean nothing on a cosmic scale, and whoever glimpses that truth, even for a moment, can never return to safe ignorance.
Lovecraft called this sensibility "cosmicism." The heart of the horror is not malice but indifference — the most terrifying thing is not a being that hates us, but one that does not notice us at all.