The first ecumenical council was the Council of Nicaea. The Nicene Fathers believed that Jesus is eternal and has the same essence as God. The Arians argued that Jesus was created and not eternal, using scripture references. The Nicene Fathers also emphasized that Jesus is of the same nature as God. These were the main points discussed at the Council of Nicaea.
So the first ecumenical council was the Council of Nicaea. The two points articulated by the Nicene Fathers were that Jesus is eternal with God and Jesus is the same essence as God. When we say eternal with God, one of the issues was whether or not Jesus was created. The Arians said there once was when he was not, and they argued John 3, 16 says that Jesus was begotten, so that must mean he's not eternal. They translated Colossians 1, 15 to say that Jesus was the firstborn of all creation, that he was a part of the creation, so he's created, he must not be eternal.
So their Greek version of Proverbs 8 said that wisdom was created. So if Jesus is the wisdom of God, and the Bible says that was created, then Jesus must be created, and therefore must not be eternal with God. So you can see that they argued from scripture, and we'll respond to this in a second, but you can see that they denied that Jesus is eternal with God. The Nicene Fathers also maintained that Jesus is the same essence as God.
So Hebrews 1, 3 uses the word essence, the Greek is hypothesis, or hypostasis, and it clearly says that he's the exact representation of the Father's essence. But the Arians have said that he can't be of the same nature, since God is one, and God is uncreated, and therefore if Jesus is created, then he can't be God, he can't be of the same essence as God. So these are the two issues that the Nicene Fathers stood for, Jesus is eternal with God, and Jesus is the same essence as God.
