The Cetagandans sought to perfect the human genome; everyone knew that. But nobody considered what might happen when they had.
Count your Stone-Lords, two, three, four
Haughty Lady at the door
Close your eyes and turn your head
Or her face will strike you dead.
A thousand years after the Great Migration, when the Old Tech was all but gone, the truth about the Enemy from whom our forebears fled was lost to all but myth and children's rhymes. Cantra Yos'Phelium's logs were preserved by Korval, but Cantra had not written of things that everyone knew. Nor had she recorded things unknown to her. No one knew the homeworld of the Enemy. It was almost irrelevant. Attacking their homeworld would not have stopped them. Nothing could stop them. They destroyed whole starsystems; the defenders could merely die. Desperate attempts to produce gene-altered super-soldiers could not breed troops that compared to the powers of the Enemy. Descendants of humanity the Enemy might be, but they were perfect, and all things that were less than perfect were anathema to them, filth to be cleansed from the universe.
What else could we do but flee?
Etta Setta climb so high
Tore the stars from out the sky.
Etta Setta delve so deep
Make us talk while we're asleep.
Etta Setta roam so wide
We can find no place to hide.
Hide behind the dragon's tree;
Dragon flies to set us free.