St. Gregory was a hero of Novigrad living in the 10th century who was declared a saint after saving the city from a horrible famine by sacrificing half his fortune to import food from the Kingdom of Nazair. The Bridge connecting Temple Isle with the rest of Novigrad is named after him. Is it not clear if it is the same person which was mentioned in the first game - an inquisitor, author of litany, who, according to legend, died in the ancient crypt after defending himself from the heretics.