Lopez, Eneko: A Basque cleric and ecclesiastical magician
Manfred, Earl of Carnac, Marquis of Rennes, Baron of Ravensburg: nephew of the Holy Roman Emperor
Marina, Dottore Luciano: Strega Grand Master, wearer of the Winged Mantle
Montescue, Katerina : heiress to the bankrupt House Montescue. Works as a smuggler.
Valdosta, Benito: grandson of the Duke of Ferrara; a pickpocket while in hiding.
Valdosta, Marco: grandson of the Duke of Ferrara; a skilled doctor and powerful mage; heir to House Valdosta and the Lion Crown
Winged Lion of Venice: the city's ancient guardian; answers only to the wearer of the Winged Mantle.
History
Point of divergence
In our own universe, Hypatia of Alexandria was killed for her non-Christian views, shortly before the destruction of the Library by an angry mob. In this universe, Hypatia was converted to Christianity by John Chrysostom, and stopped the mob from destroying the Library. She continued her correspondence with John and St. Augustine, which eventually led to the modern divisions of the Church. The Library was a great storehouse of magical knowledge—the inference being that the information was lost to us in this universe when the Library was destroyed. In this universe, while magic is not commonplace its existence is no secret to the general populace and is practiced by those with the inborn power and/or discipline to use it. Notably, the clergy utilize elemental magic.
Church in Europe
Petrines
Led by the Grand Metropolitan in Rome, the Petrine branch of the Church is the creed of choice in Italy and Spain, with a relatively large following in Aquitaine. The Petrines are noted for taking a mediative role in politics and a more tolerant attitude to other faiths.
Paulines
Most of central and northern Europe follow the Pauline creed. The Paulines are recognized for a general intolerance to all non-Christians, though some members of the Church are more politic about it than others. There is no official head of the Pauline church, though the Holy Roman Emperor is the "Bulwark of the Faith".
Ferrara: Like Venice, the Ferrarese are politically non-aligned, and they serve as agents to both the Empire and the Grand Metropolitan. Duke Enrico Dell'Este, grandfather of Marco and Benito, is known as the Old Fox.
Genoa: The only rivals of the Veneze on the open seas, in terms of both trade and navy.
Milan: The Milanese and the Visconti house are the leaders of the Motagnards, who are bent on the Empire annexing northern Italy. They are oblivious to the fact that this is the last the thing Empire wants. Caesare Aldanto hails from Milan.
Venice: the most trade-oriented and tolerant city in Europe.
Verona: Venice's land-based rival
Others
Aquitaine: A realm that encompasses most of our universe's France and England. Francesca de Chevreuse hails from the southern capital, Orleans.
Holy Roman Empire: Ruling over all of central Europe, including Austria, Germany, and Denmark, the Empire is the most powerful nation in Europe, and adheres to the Pauline creed. Manfred of Brittany is an heir to the Empire, currently ruled by Charles Fredrik Hohenstauffen.
League of Armagh: A coalition of Celtic states. Most of their territory lies in the British Isles. Manfred of Brittany is the heir to a part of the League as well as the Empire.
The novels
The Shadow of the Lion by Mercedes Lackey, Eric Flint & Dave Freer
This Rough Magic by Mercedes Lackey, Eric Flint & Dave Freer
A Mankind Witch by Dave Freer
Much Fall of Blood by Mercedes Lackey, Eric Flint & Dave Freer
Burdens of the Dead, by Mercedes Lackey, Eric Flint, and David Freer.
All the Plagues of Hell, by Eric Flint and Dave Freer.