In Arthur C. Clarke’s Childhood’s End, the alien overlords are called the Overlords.
The Overlords arrive above Earth and assume control of international affairs while presenting themselves as guardians of humanity. Their rule ends war, poverty, disease, and environmental destruction, creating an apparent golden age. However, their supervision comes at the cost of human independence, creativity, and eventually humanity’s continued existence as a separate species.
The chief Overlord is Karellen, who serves as the “Supervisor for Earth.” For decades, the aliens conceal their physical appearance. When they finally reveal themselves, they resemble the traditional Western image of devils, complete with horns, wings, and tails. That revelation explains why Clarke made their benevolent public role so unsettling.
The Overlords are not the ultimate power behind the transformation. They serve the Overmind, a vast cosmic intelligence, and act as a bridge species that helps developing civilizations evolve toward collective consciousness. “Time Lords,” “Vulcans,” and “Martians” belong to other fictional universes or traditions, not Clarke’s novel.