I've read the entirety of HP Lovecraft's work. "At the Mountains of Madness" discusses Antarctica being both a frozen tomb of ancient beings as well as a pathway beyond our reality. Maybe his nightmares revealed horrifying truths of reality. I know that while I was reading through the collection the first time, I began to feel an overwhelming existential dread, as if the oppressive horrors that taunted Lovecraft had reached through the pages and through time to afflict me with their cold, hope-draining touch.