According to these scraps of information, the basis of the fear was a horrible elder race of half-polypous, utterly alien entities which had come through space from immeasurably distant universes and had dominated the earth and three other solar planets about six hundred million years ago. They were only partly material — as we understand matter — and their type of consciousness and media of perception differed wholly from those of terrestrial organisms. For example, their senses did not include that of sight; their mental world being a strange, non-visual pattern of impressions. They were, however, sufficiently material to use implements of normal matter when in cosmic areas containing it; and they required housing — albeit of a peculiar kind. Though their senses could penetrate all material barriers, their substance could not; and certain forms of electrical energy could wholly destroy them. They had the power of aërial motion despite the absence of wings or any other visible means of levitation. Their minds were of such texture that no exchange with them could be effected by the Great Race.
When these things had come to the earth they had built mighty basalt cities of windowless towers, and had preyed horribly upon the beings they found. Thus it was when the minds of the Great Race sped across the void from that obscure trans-galactic world known in the disturbing and debatable Eltdown Shards as Yith. The newcomers, with the instruments they created, had found it easy to subdue the predatory entities and drive them down to those caverns of inner earth which they had already joined to their abodes and begun to inhabit. Then they had sealed the entrances and left them to their fate, afterward occupying most of their great cities and preserving certain important buildings for reasons connected more with superstition than with indifference, boldness, or scientific and historical zeal.
But as the aeons passed, there came vague, evil signs that the Elder Things were growing strong and numerous in the inner world. There were sporadic irruptions of a particularly hideous character in certain small and remote cities of the Great Race, and in some of the deserted elder cities which the Great Race had not peopled — places where the paths to the gulfs below had not been properly sealed or guarded. After that greater precautions were taken, and many of the paths were closed for ever — though a few were left with sealed trap-doors for strategic use in fighting the Elder Things if ever they broke forth in unexpected places; fresh rifts caused by that selfsame geologic change which had choked some of the paths and had slowly lessened the number of outer-world structures and ruins surviving from the conquered entities.
The irruptions of the Elder Things must have been shocking beyond all description, since they had permanently coloured the psychology of the Great Race. Such was the fixed mood of horror that the very aspect of the creatures was left unmentioned — at no time was I able to gain a clear hint of what they looked like. There were veiled suggestions of a monstrous plasticity, and of temporary lapses of visibility, while other fragmentary whispers referred to their control and military use of great winds. Singular whistling noises, and colossal footprints made up of five circular toe-marks, seemed also to be associated with them.
It was evident that the coming doom so desperately feared by the Great Race — the doom that was one day to send millions of keen minds across the chasm of time to strange bodies in the safer future — had to do with a final successful irruption of the Elder Beings. Mental projections down the ages had clearly foretold such a horror, and the Great Race had resolved that none who could escape should face it. That the foray would be a matter of vengeance, rather than an attempt to reoccupy the outer world, they knew from the planet’s later history — for their projections shewed the coming and going of subsequent races untroubled by the monstrous entities. Perhaps these entities had come to prefer earth’s inner abysses to the variable, storm-ravaged surface, since light meant nothing to them. Perhaps, too, they were slowly weakening with the aeons. Indeed, it was known that they would be quite dead in the time of the post-human beetle race which the fleeing minds would tenant. Meanwhile the Great Race maintained its cautious vigilance, with potent weapons ceaselessly ready despite the horrified banishing of the subject from common speech and visible records. And always the shadow of nameless fear hung about the sealed trap-doors and the dark, windowless elder towers.
V.
That is the world of which my dreams brought me dim, scattered echoes every night. I cannot hope to give any true idea of the horror and dread contained in such echoes, for it was upon a wholly intangible quality — the sharp sense of pseudo-memory — that such feelings mainly depended. As I have said, my studies gradually gave me a defence against these feelings, in the form of rational psychological explanations; and this saving influence was augmented by the subtle touch of accustomedness which comes with the passage of time. Yet in spite of everything the vague, creeping terror would return momentarily now and then. It did not, however, engulf me as it had before; and after 1922 I lived a very normal life of work and recreation.