Short answers, pulled from the story.
Gregory of Nazianzus, also known as Saint Gregory the Theologian or Gregory Nazianzen, was an early Roman Christian theologian and prelate who served as Archbishop of Constantinople from 380 to 381. Born around 329 in southwest Cappadocia, he is widely considered the most accomplished rhetorical stylist of the patristic age.
Gregory of Nazianzus was designated Theologus, or Theologian, by the Council of Chalcedon in 451. He is one of only three men in the life of the Orthodox Church granted that epithet, the others being John the Apostle and Symeon the New Theologian.
Gregory of Nazianzus defended the Nicaean doctrine of homoousia, the consubstantiality of the Son with the Father, against Arian positions. He was the first to use the idea of procession to describe the relationship between the Holy Spirit and the Godhead, and Paul Tillich credited him with creating the definitive formulae for the doctrine of the Trinity.
Gregory of Nazianzus is known as one of the Cappadocian Fathers along with the brothers Basil of Caesarea and Gregory of Nyssa. He met Basil as a fellow student in Athens, and the two became lifelong friends and collaborators in defending Nicene orthodoxy.
Gregory of Nazianzus resigned during the First Council of Constantinople in 381 after Egyptian and Macedonian bishops refused to recognize him, arguing his transfer from the See of Sasima was canonically illegitimate. Physically exhausted and fearing he was losing the confidence of the bishops and the emperor, he chose to step down rather than deepen the division.
The relics of Gregory of Nazianzus are now enshrined in the Patriarchal St. George's Cathedral in Istanbul, in the Fanar. They were returned to Istanbul by Pope John Paul II on the 27th of November 2004, after having been taken to Rome by Crusaders during the Fourth Crusade in 1204.