In what manner is Arianism associated with the Council of Nicaea?
Arainism was the reason the first Ecunemical Council (Nicea) was called together. Constantine wanted to counter this heresy. Arianism, formed by Aryius, preached that Jesus was lesser than the Father. The response was exiling him and forming the Creed (i beleive in one God, the father…) to reaffirm faith, I dont know about liturgy of the Romans.