ARISIANS

Peaceful humanoid species that have developed what could be among the first sentient civilisation in our universe. They have forgone physical and developed tremendous mental power. Foreseeing the invasion of our universe by the Eddorians, a species from another universe, they began, over 2 billion years ago, a covert breeding program on every world that can produce intelligent life, with the aim of producing a means to eventually destroy the Eddorian race. Their work done, their plans are to remove themselves from the universe.
Source: E.E. "Doc" Smith, Triplanetary