"The Creature From Beyond Infinity e-book of a 1940 novella whose copyright expired about 40 years ago."

“They dare'd not invade the palace while the globe shone, for the light-rays would have killed them. … This island-continent would have gone down beneath the sea long ago if I hadn't pitted my magic and my science against that of the children of Dagon. They are masters of the earthquake, and Atlantis rests on none too solid a foundation. Their power is sufficient to sink Atlantis forever beneath the sea. But within that room" — Zend nodded toward the curtain that hid the sea-bred horrors — "in that room there is power far stronger than theirs. I have drawn strength from the stars, and the cosmic sources beyond the universe. You know nothing of my power. It is enough — more than enough — to keep Atlantis steady on its foundation, impregnable against the attacks of Dagon's breed. They have destroyed other lands before Atlantis.”

“The words. I couldn’t understand the words. The only means of communication, and they are a deadly barrier.”

“The wars ended when there were no longer two societies left to fight against each other.”

“Then I knew that the last test of sanity had failed me, for it was no longer possible to tell the unreal from the real. The last test fails when the illusion moves into life itself and you can touch and feel and handle the commercial vision as if she were the real woman. There was no defense any more.”

“All these things were slipping away from him, in a clear, cold wisdom that came from beyond the stars. He envisioned man as a bit of animate clay moving fro a little while upon a ball of mud and stone and water that drifted through the void, through the darkness that would finally engulf it.”

“Henry Kuttner profile at Fantastic Fiction”