I have tried and failed to solve the mystery of the Historical Arthur. I feel much more qualified however to talk about the Arthur of fiction.
Whatever the real story of Arthur was, his legend has been influenced by many factors, including Celtic pagan mythology, and also by the contemporary concerns of various authors from the Crusades to the War of the Roses to the present.
As most Arthurian authors until the very modern age have been Christians of some type, it's safe to say Biblical themes have been an influence.
Given Gildas debatable relationship to Arthurian tradition. I could start by mentioning how he references the Beasts of Daniel 7 and Revelation 12-13 to insult 5 local kings. So the Bear reference is not at all evidence Cuneglass or Owain was normally called the Bear/Arth/Arto.
Of most interest however are the most notorious Kings of The Bible, like David and Solomon. In many cases even if mimicking David wasn't the origin of a certain plot point the similarity could have still been in some authors' minds. And it's fun to look at parallels that may or may not have been intentional at all.
Davidic parallels for the Mythical Arthur could begin right with his origin story. Uther's adultery with Igerne and murder of Goloris could be compared to Bathsheba and Urias, but how it plays out is very different. Recently that Starz series Camelot inverted the usual Arthur-Guinevere-Lancelot triangle by making Arthur the adulterer, that makes a David and Bathsheba parallel very possible to see, but the Lancelot replacement isn't murdered by Arthur, though he does die in battle as Urias technically does.
David had two sons who were would-be usurpers like Mordred. And with Absalom the story does begin with half-brother/half-sister incest, (but the real Sin there was the Rape).
And going back to the original version where Mordred was Arthur's sister's son, you could compare him to Joab son of Zeruiah who was the real mastermind of Adonijah's attempted coup. And like Mordred, Joab wasn't David's only maternal Nephew, he had two brothers, Abishai and Ashael and David's other sister Abigail was the mother of Amasa who was Absalom's commander in chief. So both rebellions involved a son and a sister's son, which is interesting.
There is also debate among scholars on if David's sisters were by the same father, an issue I'm still investigating myself.
Also both these rebel sons had lain with or attempted to marry Concubines of David, which possibly parallels Mordred's marrying Guinivere, though she was the Queen-Wife not a Concubine.
But what I mainly want to talk about today is Perceval.
Chretien de Troyes' Perceval, le Conte du Graal, which was the first appearance of both Perceval and The Holy Grail. Had a number of influences on it no doubt, but one thing I've noticed is a possible allegory in which Perceval is David and Arthur is Saul.
Many later details we associate with Perceval weren't there yet, he is not given a detailed genealogy for one thing, he could be a complete commoner for all we know. Also none of the people or places directly linked to the Grail are named yet.
Perceval first makes a name for himself by killing a Knight who was troubling Arthur, that could be compared to slaying Goliath, and Sir Kay's role could be Abner. While this isn't part of Chretien's narrative, it's interesting that when Arthur is given a humble background prior to becoming King, it's usually as something like a farmer (as in Disney's Sword in The Stone), which would fit Saul more then David who was a Shepherd.
And even though their relation to each other is different and to Arthur non existent. I think maybe Gornemant and Blanchefleur could be Johnathon and Michal.
The big thing though is, I think The Fisher King might be based on Ahimelech.
The figure of The Fisher King I have seen described before as being like a Priest-King, now at face value in Biblical history that makes us think of Melchizedek, the Hasmoneans and if you're a Christian Jesus. But what's interesting about Ahimelech is he was a Priest but his name has the Hebrew word for King in it. The question is if Chretien could have known that?
I've mentioned before how The Holy Grail was not originally identified as the Cup at the Last Supper, it was the third known Grail Romance author, Robert de Boron, that first made that identification. In Chertien it seems to be a plate or bowl of some kind that contained a single Mass Wafer. What that means is there was a thematic at least Last Supper connection, but it was to the Bread not the Wine. But it should be noted in the original French text Chertien call is "un Graal" or "A Grail" not "The Grail", so it probably never was his intent to say it's the original of anything.
To a Christian, all references to bread, especially unleavened bread throughout the Old Testament are seen as anticipating the Bread of the Last Supper and probably representing the same thing, starting with the Bread and Wine offered by Melchizedek. This would particularly be true of the Table of Shewbread in the Holy Place of the Tabernacle. So it's interesting that Ahimelech offers David the bread of the Table of Shewbread.
The Grail Procession in Chretien also includes a Candelabra which could stand in for the Menorah, though it had 10 candles rather then 7. The Menorah isn't specifically mentioned in the Ahimelech account but it's the Tabernacle so it would have been there.
The Fisher King also gives Perceval a Sword. Ahimelech gives David the Sword of Goliath which had been kept with the Ephod since David slew him.
That Gwain takes over the narrative I think is where this parallel ends.
Chertein's tale was unfinished, so we don't know if Perceval would have gone on to become a King as he often does in later Grail romances.
Chertein also invented the character of Lancelot in an earlier different work, but that Lancelot was never part of the Grail story, there was no Galahad or Elaine of Corbenic yet.
The second Grail Romance was Wolfram von Eschenbach's Parzival. Wolfram's work is very well known, yet strangely later Grail and Arthurian romances really didn't follow his lead. They have in common adding a genealogical link to the Grail family for Percival, but elsewhere it's usually through his father while for Wolfram it was through his mother. The Vulgate cycle and Malory give completely different names for Percival's ancestors and the Grail family. And the characters of Belacane and Feirefiz do not reappear either.
The one possible influence is that once Lancleot became part of the Grail story and Galahad is created, I think he takes on some aspects of Feirefiz. With Elaine of Corbenic replacing Repanse de Shoye. And Prester John becoming Galahad.
There are a lot of clearly intentional historical anachronisms in Wolfram. I as a student of Bible Prophecy disagree with seeing Babylon as code for Rome in 1 Peter or Revelation, but that idea was firmly established by Wolfram's time, and that one of his rulers of Babylon has a clearly Roman name, Pompeius, tells me that Wolfram meant Babylon to be code for Rome. But he probably had the Eastern Empire in mind, what we call the Byzantine Empire never called itself that, they always called themselves Romans. It's the same with references to Rome and Romans in old Isalmic writings.
I've talked before briefly about how the Grail is a Stone in Wolfram, and about Graham Hancock's theory that Wolfram's Grail was the Ark of the Covenant (which contained stone tablets), and that Wolfram was aware of Ethiopia's claim to have the Ark. I'm convinced of much of that argument, but I do take things from people like Hancock with a grain of salt.
There are many thematic reasons to still link the Ark with the Grail even after the Grail becomes the Cup of the Last Supper. Jesus quotes Exodus (but not the Passover account, rather Exodus 24:8) at the Last Supper, the Blood of Oxen was shed to confirm the Old Covenant, and the Blood of Jesus is shed to confirm the New and Everlasting Covenant. So the Grail could be seen as the Ark of the New Covenant.
Robert de Boron also introduced the Seige Perilous (The Perilous Seat) as a special Seat at the Round Table linked to the Grail, that only the worthy Grail King can sit on it. The lid of the Ark is called thanks to translation errors The Mercy Seat and is mistakenly believed by many today to be a Throne, specifically the Throne Jesus will sit on when He returns. And if someone unworthy sat in the Seige Perilous it killed them, like how the Ark killed unclean people who touched it.
Even the idea of the Grail catching the Blood of Jesus shed after he was pierced with the Spear is interesting. Ron Wyatt and Michael Rood believe the Ark was located under Golgotha and that Jesus Blood fell through the cracked open ground onto the Mercy Seat. In my Mercy Seat study I was very critical of that view. But the logic behind it stems from Leviticus 16 and Yom Kippur.
The first King of the Grail line in Robert de Boron is named Bron. That name serves a dual purpose I think. One is to echo the Celtic Bran linked to the Cauldron that played the Grail's role in the Welsh Arthurian tales. But it is also stated in de Boron that the full name of Bron was Hebron. Hebron is a name who's most well known Biblical usage is as a city (Judah and David's capital before Jerusalem), but it's also the name of a leader of the Kohathites in Exodus 6:8 and Number 3:19&27 who were in charge of caring for The Ark and other Tabernacle vessels in Numbers 3:30-32.
Bron married a Sister of Joseph of Arimathea, named Enygeus. Robert de Boron's narrative is to me very interesting, considering I have argued that Joseph of Arimathea was Jesus' half brother Joses. And that one of Jesus half sister's was named Naomi and became ancestral to the Bagratid dynasty possibly via marrying someone of the royal family of Adiabene. And that The Virgin Mary might have had Hasmonean ancestry. I doubt de Boron believed similar things, but they are interesting reasons for me to consider doing my own re-imagining of de Boron's narrative.
I also wonder if the story of King Kalafes suffering from Leprosy and being healed by the Grail, then converting to Christianity, was based on the legend about King Abgar of Edessa. I of course take issue with Eisenman's theories. Also interesting is the theory that a later Abgar of Edessa, was the real basis of Lucius of Britain with where he lived being a scribal error.
One more Biblical figure I think of as possibly linkable to the Wounded King, is King Asa. Asa was one of the longer reigning kings of Judah, over 40 years, and one of the better reviewed ones. But because of one of his mistakes he spent the twilight of his reign with a crippling foot disease. The last few years of his reign his successor Jehoshaphat was already ruling as Co-Regent. Which fits how the Fisher King and Wounded King are sometimes separate with the Fisher King as the son. The era in which Jehoshaphat lived I discus on my Revised Chronology Blog.
Still we should not forget however that the figure of the Fisher King definitely has a Pagan origin too going back to the Welsh Bran the Blessed. One thing the 80s Excalibur film gets criticized for is making Arthur the Fisher King, and it's generally defended only by saying it's the best way to condense all of Arthurian legend down to one film. But when you go back to the Welsh Cauldron legends, Arthur and Bran are kind of interchangeable. Both are said to be mortally wounded and waiting to be healed.
The way Excalibur depicts Arthur as all dark and Emo during his latter years does remind me of some film depictions of Solomon. From Yul Brynner to the 90s Solomon movie that sometimes airs on the Hallmark channel.