Priestess of Avalon is a 2000 novel by American writer Marion Zimmer Bradley, completed posthumously by Diana L. Paxson. It follows detailing the life of Helena, first wife of Western Roman Emperor Constantius Chlorus and mother of Constantine. Plot summary The novel begins by showing her birth, with a druid giving a prophecy of her life. It proceeds to show her as a young girl named Eilan, who becomes a priestess on the Isle of Avalon. As a young woman, the British priestess Eilan, known to the Romans as Helena, falls in love with the charismatic Roman Constantius. The Roman noble takes her away from Avalon as she is banished for this forbidden love and, before long, Helena bears him a son, who will become Constantine the Great. Helena's position in Roman society now gives her the freedom to travel about in the empire. When her son Constantine becomes Emperor, she slowly discovers brand-new roles. She faces the spread of the new Christian religion and seeks to understand the old knowledge of the goddess in light of the new religion. As Empress-Mother, Helena travels on a pilgrimage to the Holy Land to find the answers to questions that arise between the old religion and the new. Characters Eilan [Julia Coelia Helena, later, Flavia Helena Augusta] – the priestess of the story, protagonist. She is the daughter of Prince Coelius, consort of Constantius, mother of Constantine, and priestess of Avalon Constantius – the Roman noble she marries Constantine – Eilan's (Helena's) son, Emperor AD 306-37 Aelia – a young priestess, trained with Helena Arganax - Arch-Druid during Helena's youth. Atticus – Constantine's Greek tutor Ceridachos – Arch-Druid when Dierna becomes High Priestess Cigfolla – a priestess of Avalon Julius Colius [King Coel] – Prince of Camulodunum, father of Helena Corinthius the Elder – Helena's tutor Corinthius the Younger – master of a school in Londinium Crispus – Constantine's illegitimate son by Minervina Cunoarda – Helena's Alban slave Dierna – Helena's second cousin, later Lady of Avalon Drusilla – cook in Helena and Constantius's household Fausta – daughter of Maximian, wife of Constantine, and mother of his legitimate children Flavius Pollio – a kinsman of Constantius Ganeda – Helena's aunt, Lady of Avalon Gwenna – a maiden being trained on Avalon Haggaia – Arch-Druid when Helena returns to Avalon Helena the Younger ("Lena") – a noblewomen of Treveri, wife of Crispus Heron