Perlesvaus, ou, Le Haut Livre du Graal.
Perlesvaus, or, The High History of the Holy Grail
Composed 1191-1212. French
Written for Monseigneur de Nesle, by a cleric, "dans un Maison de religion dans l'ile d'Avalon"--at the building of religion of the Isle of Avalon, i.e. Glastonbury Abbey. A particularly bloody and bizarre take on the Grail legend. Take the opening sentence:
"The history of the holy vessel which is called Grail, in which the precious blood of the Savior was received on the day He was crucified in order to redeem His people from hell: Josephus set it in remembrance by annunciation of the voice of an angel, so that the truth might be known by his writing and by his testimony concerning knights and worshipful men, how they were willing to suffer pain and travail in order to exalt the law of Jesus Christ, which He desire to renew by His death and crucifixion."
As pointed out by Roger Sherman Loomis, why would the first century Jewish historian Josephus ever write about King Arthur? Or about Jesus? It gets stranger. He invokes angelic authority, has his enemies die rather gruesome deaths, and gives us a Perceval who is just short of a mass murderer, on a mission to revenge his cousin's death.
It picks up where Chretien's Perceval left off, after having failed in his visit to the Grail castle. However, in this version, he completes his quest not by asking the right question, but by killing his cousin's murderers. After he does so, he goes off to the Isle of Ageless Elders, and has a number of adventures, then returns to the castle of the Fisher King. The king dies, and Perceval places him in a coffin; in the other coffins are Nicodemus and Joseph of Arimathea. All rest in the chapel with holy relics. At this point, the grail disappears and the bodies are taken away on a boat. Now Perceval boards a boat to find them, and is never heard from again.
For a Frence Romance, it uses a lot of Irish and Welsh myth, more than one would think; it's Christianity is more in its name for God than in any sense of faith, hope, and charity.
This can be found on the web at the Berkeley Digital Library: http://sunsite.berkeley.edu/OMACL/Graal.