Trivia: There was a series made in the UK (and very popular in many other countries) in the 80's called Robin of Sherwood. One of the characters was a Saracen called Nasir. He was not originally supposed to be one of the regulars, but the actor (Mark Ryan) got on so well with the rest of the cast, the decided not to kill Nasir, but keep him on as one of Robin's men. When Robin Hood Prince of Thieves was in development, a character called Nazeem was written because the writer thought that the Saracen was a traditional part of the legend (along with Little John, Will Scarlet and Marian). The name was changed to Azeem because they found out that the character was unique to Richard Carpenter's Robin of Sherwood. So, thanks to a random piece of casting in the UK in the 80's, we were given Morgan Freeman's Azeem.
Trivia: When the villagers are pushing the catapult to the castle so they can get Robin and Azeem inside, the person on the very right of the screen is wearing the same clothes as Will and has the same hair style, but it is definitely not Christian Slater. It is his stunt double.
Trivia: There is a close relation between Sean Connery and Robin Hood. Connery played Robin Hood in the movie "Robin and Marian" in 1976. His son, Jason Connery, played this same character in "Robin of Sherwood," the TV series, in the eighties. And, finally, he had a small part in "Robin Hood: Prince of Thieves" as King Richard.
Trivia: Sean Connery donated his entire salary for his cameo to charity.
Trivia: Robin Wright was originally cast as Maid Marian, but had to withdraw just before filming as she found out she was pregnant.
Answer: The white robes, reference to "the old ways", and pentagram across the map when the Sheriff meets the Barons suggests per-Christian Druidism; the upside down crucifix certainly implies Devil-worship. These two spiritual paths are, by nature, mutually exclusive. In short, a fictional pseudo-witchcraft invented for the film, yes.