The First Council of Nicaea was a council of Christian bishops convened in the Bithynian city of Nicaea by the Roman Emperor Constantine I in AD 325.0 The council condemned Arius and the Arian heresy that Christ is a created being and revised the creed to clarify the equality of God the Father and God the Son.
The council brought together bishops from all over Christendom to resolve some divisive issues and ensure the continued unity of the church. The most significant issue was the Arian controversy, which had become so serious in the eastern half of the empire, and particularly in northeast Africa, that it was threatening the continued unity of the church there.
The council overwhelmingly affirmed the deity and eternality of Jesus Christ and defined the relationship between the Father and the Son as “of one substance.” It also affirmed the Trinity, the Father, Son, and Holy Spirit were listed as three co-equal and co-eternal Persons.
Yes the holy trinity, where as Arian churches always had 2 pillars.