The Last Monster

Irgi was the last of his monster race, guardian of a dead planet, master of the secret of immortality. It was he whom the four men from Earth had to conquer to gain that secret—a tentacled monstrosity whom Earthly weapons could not touch.
Irgi was the last of his race. There was no one else, now; there had been no others for hundreds and hundreds of years. Irgi had lost count of time dwelling alone amid the marble halls of the eon-ancient city, but he knew that much. There were no others.
Only Irgi, alone.
He moved now along the ebony flooring, past the white marble walls hung with golden drapes that never withered or shed their aurate luster in the opalescent mists that bathed the city in shimmering whiteness. They hung low, those wispy tendrils of mist, clasping everything in their clinging shelter, destroying dust and germs. Irgi had discovered the mist many years ago, when it was too late to save his kind.
He had flung a vast globe of transparent metal above this greatest of the cities of the Urg and filled it with the mist, and in it he had stored the treasures of his people. From Bar Nomala, from Faryl, and from the far-off jungle city of Kreed had he brought the riches of the Urg and set them up. Irgi enjoyed beauty, and he enjoyed work. It was the combination of both that kept him sane.
Toward a mighty bronze doorway he went, and as his body passed an invisible beam, the bronze portals slid apart, noiselessly, opening to reveal a vast circular chamber that hummed and throbbed, and was filled with a pale blue luminescence that glimmered upon metal rods and bars and ten tall cones of steelite.
In the doorway, Irgi paused and ran his eyes about the chamber, sighing.
This was his life work, this blue hum and throb. Those ten cones lifting their disced tips toward a circular roof bathed in, and drew their power from, a huge block of radiant white matter that hung suspended between the cones, in midair. All power did the cones and the block possess. There was nothing they could not do, if Irgi so willed. It was another discovery that came too late to save the Urg.