The Son was a religious figure on 892-IV, a close analogue to Jesus Christ of Earth. The central figure in the persecuted minority religion of the Children of the Son, his name came from the belief that he was the Son of God. His teachings were called the "word of the son", and emphasized total love and total brotherhood.

The Son's name was often invoked in blessings, such as "May the blessings of the Son be upon you" or "Blessed be the Son". (TOS: "Bread and Circuses")

This character was only mentioned in dialogue.
While the gods of the local natives had the same names as their Human counterparts, and he was explicitly compared to Christ by the crew, his followers only ever referred to him as the Son.