Dragon Moon by Henry Kuttner

Dust of the stars was under our feet, glitter of stars above -- Wrecks of our wrath dropped reeling down as we fought and we spurned and we strove. Worlds upon worlds we tossed aside, and scattered them to and fro, The night that we stormed Valhalla, a million years ago! -- Kipling.

The moon waxed and waned, and at last Elak awoke, on the further shore, by the cavern mouth that led to the upper world. The underground mere lay silent at his feet, still bathed in the soft green glow. In the distance the islet was, and he could make out the white outline of the temple upon it. The temple where he had slept for a month. But there was no sign of life. No shadows stirred in the depths beneath him. Yet within himself he sensed a secret well of power that had not been there before.