Biblical or Historical Devil Worshipper?
Since we are dealing with the 14th century and a fictional novel, it would be best to use a fictional
character. At least this way it remains fictional.
Why not take a medieval legend to your advantage.
It seems to me the legendary personage of Cartaphilus. Although legend says he is of Jewish origin, you could make him a Roman soldier guarding the door of Pilate, which makes more sense in an historical setting.
The Wandering Jew is a mythical immortal man whose legend began to spread in Europe in the 13th century. The original legend concerns a Jew who taunted Jesus on the way to the Crucifixion and was then cursed to walk the earth until the Second Coming. The exact nature of the wanderer's indiscretion varies in different versions of the tale, as do aspects of his character; sometimes he is said to be a shoemaker or other tradesman, while sometimes he is the doorman at the estate of Pontius Pilate.
The earliest extant manuscript with the legend is the Flores Historiarum by Roger of Wendover, where it appears in the part for the year 1228, under the title Of the Jew Joseph who is still alive awaiting the last coming of Christ.
At least from the 17th century the name Ahasver has been given to the Wandering Jew, apparently adapted from Ahasuerus 'Xerxes,' the Persian king in the Book of Esther, who was not a Jew, and whose very name among medieval Jews was an exemplum of a fool. This name may have been chosen because the Book of Esther describes the Jews as a persecuted people, scattered across every province of Ahasuerus' vast empire, similar to the later Jewish diaspora in countries whose state and/or majority religions were forms of Christianity.
A variety of names have since been given to the Wandering Jew, including Matathias, Buttadeus, Paul Marrane, and Isaac Laquedem which is a name for him in France and the Low Countries, in popular legend as well as in a novel by Dumas.
Where German or Russian are spoken, the emphasis has been on the perpetual character of his punishment, and thus he is known there as Ewiger Jude and vechny zhid (вечный жид), the "Eternal Jew". In French and other Latin languages, the usage has been to refer to the wanderings, as in French "le Juif errant", in Spanish "el judío errante" [circular reference] or in Italian "l'ebreo errante" [circular reference] and this has been followed in English from the Middle Ages, as the Wandering Jew. In Finnish he is known as Jerusalemin suutari (Shoemaker of Jerusalem), implying he was a cobbler by his trade.
Some scholars have identified components of the legend of the Eternal Jew in Teutonic legends of the Eternal Hunter, some features of which are derived from Odin mythology.
"In some areas the farmers arranged the rows in their fields in such a way that on Sundays the Eternal Jew might find a resting place. Elsewhere they assumed that he could rest only upon a plough or that he had to be on the go all year and was allowed a respite only on Christmas."
A variant of the Wandering Jew legend is recorded in the Flores Historiarum by Roger of Wendover around the year 1228. An Armenian archbishop, then visiting England, was asked by the monks of St Albans Abbey about the celebrated Joseph of Arimathea, who had spoken to Jesus, and was reported to be still alive. The archbishop answered that he had himself seen such a man in Armenia, and that his name was Cartaphilus’ a Jewish shoemaker, who, when Jesus stopped for a second to rest while carrying his cross, hit him, and told him "Go on quicker, Jesus! Go on quicker! Why dost Thou loiter?", to which Jesus, "with a stern countenance", is said to have replied: "I shall stand and rest, but thou shalt go on till the last day." The Armenian bishop also reported that Cartaphilus had since converted to Christianity and spent his wandering days proselytizing and leading a hermit's life.
Matthew Paris included this passage from Roger of Wendover in his own history; and other Armenians appeared in 1252 at the Abbey of St Albans, repeating the same story, which was regarded there as a great proof of the truth of the Christian religion. The same Armenian told the story at Tournai in 1243, according to the Chronicles of Phillip Mouskes, (chapter ii. 491, Brussels, 1839). After that, Guido Bonatti writes people saw the Wandering Jew in Forlì (Italy), in the 13th century; other people saw him in Vienna and elsewhere.
There were claims of sightings of the Wandering Jew throughout Europe, since at least 1542 in Hamburg up to 1868 in Harts Corners, New Jersey. Joseph Jacobs, writing in the 11th edition of the Encyclopædia Britannica (1911), commented "It is difficult to tell in any one of these cases how far the story is an entire fiction and how far some ingenious impostor took advantage of the existence of the myth". It has been alleged by an 1881 writer, who however cites no instances, that the supposed presence of the Wandering Jew has occasionally been used as a pretext for incursions by Gentiles into Jewish quarters during the late Middle Ages, when the legend was accepted as fact.
Another legend about Jews, the so-called "Red Jews", was similarly common in Central Europe in the Middle Ages. - Wandering Jew (Wikipedia)
Seeing the the Russian legend calls him Judas, who may wish to go with Judas Iscariot whom the Lord said it would have been better that he had never been born! After all it is fiction. Be like Dan Brown and make up your own legendary person.
You might consider Herod the Great and his son, Herod Antipas. The Great was the one who ordered the killing of Jewish infants around year 0, and his son Antipas is the one who ordered the beheading of John the Baptist.
Then again you might wish to choose one of the Luciferians of this time period also. Simply make up a character and give him a believable sounding name.
In the 13th century, a group of people called Luciferians attracted papal attention for Devil worship, and this time there can be little doubt that this is exactly what was going on. The Pope sent Conrad of Marburg, a gentleman described as a "sadistic fanatic who had been spiritual director of St. Elizabeth of Thuringia and had delighted in beating and humiliating her," to Germany in order to squash the heresy taking place there. These Luciferians believed that Lucifer and his host of demons had been unfairly expelled from heaven. Some day, they claimed, he would return and overthrow the Christian God at which time he would reign forever. They did everything they could to offend God, since their reward would be everlasting paradise with Lucifer. At least half a dozen contemporary sources give details of the Luciferians, and confessions by those accused were not made under torture.
Elements in the story of the Luciferians show further progress toward the conception of Devil worship that has been handed down to us through history. Initiates were made to kiss a toad, or sometimes a duck or goose, in either of two distasteful areas. New members also kissed a pale man who was icy cold, and in this instant they were supposed to have lost their Christian faith. There was a large feast with a huge black cat present, and those worthy of the honor kissed the cat's rear end. The candles were then extinguished, and a massive orgy ensued. After they were through with that portion of the ceremony, a man appeared from a dark comer whose bottom half was like a cat. He was given a piece of the initiate's clothing, and before he disappeared, he commended the leader of the group for his service.
There are two opinions stemming from this story concerning the Luciferians. The first is this: "This account of an initiation carries a certain conviction and it could have been stage-managed without too much difficulty." The second is: "Where a source contains untrustworthy or demonstrably false statements it should be treated with skepticism throughout; and that is the case with all the sources that tell of a Luciferian doctrine." That seems to be a case of throwing the baby out with the bath water, so to speak. The entire thesis behind the book that includes the latter statement is that witchcraft probably never existed in medieval times except for inside of the imaginations of hysterical Christians. That, according to a modem Pagan and expert in the field of witchcraft is because the author has a limited conception of what is possible in reality." She gives as as example that author's opinion that all accounts of ceremonial orgies are false, and counters with the assertion that "Orgiastic practices were a part of religious rites in many cultures of the ancient world, and are fairly widespread today." The deductive reasoning behind this being that if there were orgies in early rites, as well as in present day rites, there were most probably also orgies in medieval ceremonies, especially in light of the profuse reports of their occurrence.
Now that the Luciferians have been established with some credibility as genuine devil worshippers, we can see that there is some reason for the steadily increasing alarm with which the Church met cases of heresy.
These examples of Devil worship provide a background for what would occur in Europe over the next several hundred years. Two reasons for this second outbreak are the circulation of accounts of previous heresies involving Devil worship, and the assault on Europe by the Black Death. Since the plague was seen by many as God's punishment for their sins, it follows that people would be very interested in discovering any kind of behavior that would anger Him. With the widespread availability of theologically based discourses on how to root out possession, such as the Malleus Maleficarum (c. 1494), it was now possible for these people to be discovered and dealt with. Although the Malleus was written somewhat late to serve as an example for plague-inspired heretic elimination discourses, it is the best example of the way in which Christian authorities viewed their duties in relation to this manner of heresy.
The examples of the Paulicians, Catharists, Waldensians, and the others show how the concept of Devil worship in the Christian world grew and spread. With each new heresy, elements such as the osculum infame Devil in the form of an animal, and the ritual orgy became part of the legend, and possibly practice, of Devil worship. It is almost impossible to ascertain at this late date exactly what did happen in the Devil worship rites of the Middle ages. These people did not keep records, possibly in the interest of preserving their sacred rituals, but more probably for fear of persecution. - Devil Worship in the Middle Ages
More information can be gleaned here.