Margaret St Clair

His name was Tharg, but he was not of any life form we know today. He lived so long ago that the planet Earth had not yet shaped itself. Lava seas roiled and churned, volcanoes spouted and grew, and heavy clouds hung in the hydrogen atmosphere, leaving the planet's surface dark and dangerous. On that world Tharg met his death, or something very much like it. He became a disembodied, totally nonphysical intelligence, cut off from all contact with the life he had known.
He 'slept' for hundreds of millions of years, unconnected with the world, unthinking, hardly existing. But then he began to awake - for there was new life on Earth, creatures called 'human', and Tharg, knowing an ancient promise from the stars, had to tell them of it. But .