Nerius is the Patron Saint of Christian magi. His status as a patron saint is unofficial; he has not been canonized by the Pope. (His stats, such as they are, can be found on p91 of Realms of Power: the Divine.) According to various sources, Nerius was born in the Provencal Tribunal and he completed his Gauntlet in 941 after an apprenticeship of only five years ("Hermetic Timeline"). At a well in the Alps he entered Twilight and prayed for guidance; the archangel Michael heard him and responded, guiding him through the experience. From this point on, he "reconciled his power with God," practicing Holy Magic, and he may have been the first Holy Magus in the Order. Nerius journeyed throughout Mythic Europe spreading Holy Magic and performing feats of miraculous magic. Some of his many acts include:
Curing the sick without the use of vis.
Instantly traveling from place to place.
Changing a thing's Essential Nature.
Predicting when and where trouble would strike.
He never lost a Certamen match.
His Divine protection (he didn't use the Parma) was impenetrable to every spell.
Nerius was martyred in 1039 at the Normandy regional tribunal. One source says he came there "to urge restraint in the Schism War", but the Schism War was over by 1017, so this seems impossible ("Hermetic Timeline" places Nerius's martyrdom 35 years earlier in 1004. This would make sense with the Schism War notion, but the date was supplanted by later canon). An autobiographical account of some of St Nerius's travels does exist; this collection of twelve scrolls is in the Great Library at Durenmar (RoP:tD 91).
Valoran was Nerius's apprentice, but he vanished mysteriously. Angelus is Valoran's only known apprentice. He is old and reclusive, and lives at Cunfin, a covenant he helped to found in the Normandy Tribunal. Notably, Angelus is not a member of House Criamon; he is Ex Miscellanea. Although a "holy monk," the precise nature of his magic (is it Holy Magic with a capital H?) is unknown. Contrary to House Criamon philosophy, he believes "Twilight is a blessing bestowed by God, but to seek it out is sinful. Doing so presumes that one is worthy, while only God alone can make that judgment" (The Lion & the Lily: The Normandy Tribunal p 109).
Nerius does not appear to have wielded a Talisman. Instead, he was aided in his journeys "by a mantle given to him by his amicus, a Verditius magus named Ceylan. The mantle gave him the stamina to walk for days without eating. After Nerius's death the mantle passed to Nerius's disciple, Valoran, but both he and the mantle disappeared soon after" (RoP: tD p79). That would place Valoran's disappearance around the mid-11th century.
The Legend of Ceylan relates that he was Persian (the name is Persian for "gazelle"). He lived before the Crusades, and he came from the city where flying carpets are made (Isfahan, see Cradle & the Crescent 148). As a child he was so precocious and pious that, when he made himself a rug upon which to pray (for he was Muslim), God was so impressed that he made the rug to fly, and Ceylan rode this carpet all the way to Jerusalem. There, it is said, he was found by a Verditius on pilgrimage and taken back to his covenant, which was somewhere in Italy. There, Ceylan converted to Christianity and was taught Hermetic magic; he became one of the greatest weavers the Order has ever seen. He remained a religious man all his life, and the Mantle he gave to Nerius was his crowning achievement. He died in the Schism War.
The covenant of Fudarus, domus magna of House Tytalus, is home to the martyrdom of St Nerius, a site of pilgrimage for pious magi of the Order:
Immediately to the left of the gates of Fudarus is a clear circle of grass, marked because the area around it is blackened and blasted. This is the site of the martyrdom of St. Nerius, and has a Divine aura of 1. Every year on the anniversary of that event, a single blue flower of an unknown species blossoms in the permanently burnt sward. Several pious magi come to witness this event every year, and they do not allow anyone to pick the bloom, which lasts only one day. The magi of Fudarus do not prevent magi coming on this pilgrimage, and do not interfere with the ceremony. Some have even joined them in the past, taking part in the solemn devotions with appropriate gravitas. -- The Lion & the Lily: The Normandy Tribunal p 42
The "usual story" of the martyrdom is that a group of Tremere, Tytalus, and Flambeau magi, envious of Nerius' powers, declared Wizard's War upon him. "His Divine protection having withstood every attack, St Nerius proclaimed God's Will stronger than the petty cravings of his fellow magi, then stepped from the circle of his Celestial Immunity and died" (RoP:tD 91). The records of Tribunal meetings at Fudarus do not record the event, but with the physical evidence of the ring and blue flower mentioned previously, the only real question is the motivation and identity of the attacking magi, not the martyrdom itself.
The Priory of Saint Nerius is a Holy Society, an organization of pious magi who practice Holy Magic in Nerius's tradition. Known as Neriusians, they can be considered the most devout and sincere followers of the Saint, magi and their filia who converted to Holy Magic. Their central house is in the mountains of northern Italy (RoP:tD 94). Neriusians lobby the Church to recognize Nerius as a saint, but they keep their identity as magi secret to avoid persecution. Neriusians follow a modified version of the Benedictine rule, allowing for study and lab work, and preach religious tolerance for magical beasts and faeries, which they maintain have rational souls. They believe the Garden of Eden is in Arcadia, and that is where mankind was created. With the rise of the Franciscans, the Priory has begun adopting their Rule to allow for more travel and to live among other magi.
The Priory keeps a book containing a powerful holy rite, the Neriusian Portal, which is said to have been taught to Nerius by the angel Samuil; the book itself is a relic. This is only one of several spells which Nerius invented or discovered, and which the Neriusians keep and share among themselves (RoP:tD 94).
The Peruchia of Nerius is a small covenant of Neriusians in Hibernia. They live on the island of Little Saltee, and no women are permitted on the island. The founder and original princeps of the Peruchia, Fedelmid Ex Miscellanea, recently traveled to Qui Sonant Pro Quieto and was buried there. Indrechtach, his filius, has inherited the covenant. The Peruchia's catach is the skeletal hand of Nerius, a relic that creates a Divine aura of 3 in its immediate vicinity.