Who are the main deities in the religion of Christianity?

Answer 1

The only deity in Christianity today is God. However, the Nicene Creed of 325-381 CE defined God as a remote and ineffable Holy Trinity, who is God the Father, Jesus Christ (God the Son) and the Holy Ghost, one God and indivisible.

This was different in early times. Christianity was divided into perhaps roughly equal proportions of proto-Catholic-Orthodox and Gnostic followers. The Gnostics also believed in the Demiurge (literally: "Craftsman") who created the world. Some (not all) Gnostics believed that the Demiurge was the God of the Old Testament, who was so concerned with demanding that people worship him, he was unaware that there was a far superior God above him. When the superior God wanted to free the world from the clutches of the Demiurge, he sent Jesus. Jesus had to be disguised as a humble man, so that he could perform his mission before the Demiurge and his archons wer able to stop him.

Some smaller modern Christian denominations do not believe in the Holy Trinity. The answer to this question, that would be applicable to these groups, is simply God (God the Father).

One modern Christian denomination, the Mormon Church (Church of Jesus Christ of Latter Day Saints), believes in a plurality of gods, but that we only need concern ourselves with the Holy Trinity.