The alien race in Arthur C. Clarke’s Childhood’s End is called the Overlords. They arrive above Earth’s major cities and take control of human affairs, promising peace, prosperity, and an end to war without initially revealing what they look like.
The novel, published in 1953, follows humanity’s transformation under their supervision. The Overlords are led by Karellen, the Supervisor for Earth, who eventually reveals that they resemble the traditional Western image of demons, complete with horns, wings, hooves, and tails. Their appearance explains why Clarke delays their public unveiling for decades.
The Overlords are not simply conquerors. They serve the Overmind, a vast cosmic intelligence, and act as a bridge species that guides civilizations toward joining it. Their intervention creates a peaceful human society, but it also ends human individuality and culture when children begin developing powerful psychic abilities. A common mix-up is calling them the villains; Clarke presents them as benevolent custodians whose help carries an existential cost.