The Xeelee are a godlike species from the Xeelee Universe. They are considered to be the most advanced of all baryonic life-forms and possess technology and abilities far beyond other space-faring civilizations. They have demonstrated the ability to routinely construct Closed Time Curves and have engineered their own evolution and history as far back as 20 billion years ago (within two hundred million years of the Big Bang).
Although the Xeelee seldom directly appear or take action, their impact on the development of most civilizations and the universe as a whole is profound. The Xeelee frequently leave behind derelict ships, tools, and other materials giving the appearance of thoughtlessness or reckless abandon at what a younger species might do with it. Most younger species see no benefit in developing a technology on their own when they can simply steal it from the Xeelee debris. This has a profound influence on the various galactic economies and technological development of younger species.
They are in a war with a race of dark matter creatures known as the Photino Birds for billions of years for the continuation of all of baryonic existence.