One of the central concepts the 'cosmic horror' writer H.P. Lovecraft loved to revisit in his works was the dawning of realization of the immensity of the universe, and that this massive size means that almost everything that could happen, including the most grotesque and abominable, has happened.
Almost all things are permitted, and they probably have happened, because the universe is so large that it caters for almost all possibilities. This means that everyone's nightmares are practically real, and that they have happened somewhere, sometime. The most grotesque and hideous monsters populate the universe, committing the most abominable acts (god knows humanity has contributed its share of the abominable). The grotesque characters of Lovecraft's imagination are not necessarily real life, but they might as well be, because something as bad as them has probably happened or will happen at some point in the massive, sprawling starscape vistas of the universe.
Lovecraft created a pantheon of cosmic god-like entities who are not so much gods, as other beings that are beyond our comprehension. They may enslave or consume other species, or most often just ignore them as we would an amoeba, while the mind of the observer breaks and descends onto madness.
H.P. Lovecraft, The Call of Cthulhu
If I say that my somewhat extravagant imagination yielded simultaneous pictures of an octopus, a dragon, and a human caricature, I shall not be unfaithful to the spirit of the thing. A pulpy, tentacled head surmounted a grotesque and scaly body with rudimentary wings... It represented a monster of vaguely anthropoid outline, but with an octopus-like head whose face was a mass of feelers, a scaly, rubbery-looking body, prodigious claws on hind and fore feet, and long, narrow wings behind. This thing, which seemed instinct with a fearsome and unnatural malignancy, was of a somewhat bloated corpulence.
H.P. Lovecraft, The Dream-Quest of Unknown Kadath
Outside the ordered universe [is] that amorphous blight of nethermost confusion which blasphemes and bubbles at the center of all infinity—the boundless daemon sultan Azathoth, whose name no lips dare speak aloud, and who gnaws hungrily in inconceivable, unlighted chambers beyond time and space amidst the muffled, maddening beating of vile drums and the thin monotonous whine of accursed flutes.
H.P. Lovecraft, Through the Gates of the Silver Key
It was an All-in-One and One-in-All of limitless being and self—not merely a thing of one Space-Time continuum, but allied to the ultimate animating essence of existence's whole unbounded sweep—the last, utter sweep which has no confines and which outreaches fancy and mathematics alike. It was perhaps that which certain secret cults of earth have whispered of as YOG-SOTHOTH, and which has been a deity under other names; that which the crustaceans of Yuggoth worship as the Beyond-One, and which the vaporous brains of the spiral nebulae know by an untranslatable Sign…
Lovecraft never conceived of them as supernatural; but extraterrestrials who understand and obey a set of natural laws, which to human understanding seem magical. These beings (the Great Old Ones, Outer Gods and others)—though dangerous to humankind—are portrayed as neither good nor evil, and human notions of morality have no significance for these beings. Indeed, they exist in cosmic realms beyond human understanding. As a symbol, this is representative of the kind of universe that Lovecraft believed in.
Lovecraft considers these imaginative descriptions to be close-enough approximations to what is indeed out there somewhere, simply because of the sheer vastness of the universe. This realization, if you really feel it, brings a crushing terror and if you think about it too much, possibly madness. He proposed that its horror is measureless, and we would be better off not comprehending it.
H.P. Lovecraft, The Call of Cthulhu
We live on a placid island of ignorance in the midst of black seas of infinity, and it was not meant that we should voyage far. The sciences, each straining in its own direction, have hitherto harmed us little; but some day the piecing together of dissociated knowledge will open up such terrifying vistas of reality, and of our frightful position therein, that we shall either go mad from the revelation or flee from the deadly light into the peace and safety of a new dark age.
Similar ideas have been proposed from more scientific sources, although they tend to focus more on power differentials as a result of a technology and less on colourful descriptions of cosmic horror.
Michio Kaku, Impossible science
Imagine walking down a country road, and meeting an ant hill. Do we go down to the ants and say, "I bring you trinkets. I bring you beads. I give you nuclear energy and biotechnology. Take me to your leader?" Or we have the urge to step on a few of them?? […]
If ants in an ant hill detect a 10-lane superhighway being built near them, would they understand how to communicate with the workers? Would they assume that the workers communicate only on ant frequencies? In fact, the ants are so primitive that they would not even understand what a 10-lane superhighway was.
I think it's an awful idea to advertize our existence in space, without understanding the motives and intentions of possible alien civilizations.
Remember what happened to Montezuma and the Aztecs when they encountered Cortez and his band of cutthroats. Within a few months, the great Aztec civilization was demolished, and Cortez only had technology a few centuries at most ahead of the Aztecs. Imagine what would happen if we met a civilization a million years ahead of us. Instead of David vs. Goliath, it would be a fruit fly versus Goliath […]
Also, the main danger faced by ants confronting workers building a 10 lane superhighway is not that the workers want to eat the ants or conquer and enslave them. The main danger faced by the ants is that they will be paved over. Think of most animals in a forest. The main danger they face is not that humans will shoot them and eat them. No, the main danger is that humans will rob them of their habitat, and they will die as a consequence, even if the humans are not aware of this.
So we may live in a universe where even the most wild fiction may turn out to be true. Perhaps even dreams are not fanciful, but are interpretations of very real possibilities that have occurred somewhere, sometime.
Unknown artist, Cthulu
Unknown artist, Azathoth
Unknown artist, Nyarlathotep
Steve Somers, Yog-Sothoth