Eusebius of Nicomedia
Eusebius was bishop of Nicomedia and then of Constantinople from 339 up to his death.
Distantly related to the imperial family of Constantine, he not only owed his removal from an insignificant to the most important episcopal see to his influence at court, but the great power he wielded in the Church was derived from that source. With the exception of a short period of eclipse, he enjoyed the complete confidence both of Constantine and Constantius II.
Like Arius, he was a pupil of Lucian of Antioch, and he probably held the same views as Arius from the very beginning. He afterward modified his ideas somewhat, or perhaps he only yielded to the pressure of circumstances; but he was, if not the teacher, at all events the leader and organizer, of the Arian party.
At the First Ecumenical Council at Nicaea, in 325, he signed the Confession, but only after a long and desperate opposition. His defense of Arius angered the emperor, and a few months after the council he was sent into exile. After the lapse of three years, he succeeded in regaining the imperial favor; and after his return in 329 he brought the whole machinery of the state government into action in order to impose his views upon the Church.
Eusebius baptised Constantine the Great in 337 just before the death of the Emperor.