A brotherhood of escaped slaves and pacifists on a world where Rome never fell, whose devotion turns out to be to the Son of God rather than the sun.
The Children of the Sun are a religious community encountered in the Original Series episode Bread and Circuses, on a planet where a Roman-style empire has survived into a twentieth-century level of technology.
Made up largely of runaway slaves, they preach peace and brotherhood and live in hiding from the authorities. Their elder Septimus was once a senator, and Flavius Maximus was a celebrated gladiator before he refused to kill any more. Flavius helps Kirk, Spock and McCoy search for the survivors of the SS Beagle and dies trying to save them in the arena's cells.
Spock is puzzled that sun worshippers should hold such gentle beliefs. Uhura, who has been monitoring broadcasts, explains at the end that they worship not the sun in the sky but the Son of God.