Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is another version of the well-known story of Robin Hood (Kevin Costner) and Maid Marian (Mary Elizabeth Mastrantonio) and Robin's band of men in Sherwood Forest robbing the rich to give to the poor, and rebelling against the Sheriff of Nottingham, and all that. They spice the story up a bit by showing Robin fighting in the Crusades the returning to England with Azeem (Morgan Freeman) a Moor, and with Marian showing her skills at sword fighting. Kevin Costner's American accent is out of place, but it's better than a bad English accent.
The Sheriff of Nottingham here (Alan Rickman) is a lecherous devil-worshipper who keeps an ancient witch in a dimly-lit dungeon full of water, hopping toads, skulls and bones, taxidermied animals, and bats in cages. She calls him down to the dungeon to read his future. She pulls a round metal plate out from under a snake that was crawling through an animal skull, then she puts the plate on the floor, shoos away a couple of toads, then cracks an egg full of blood onto the plate and rolls some dice that tell his future.
That's all we see of the snake. Every time we descended back into the dungeon I hoped to see it again, but that never happened. It was just a cameo. But it's a snake in a skull, so it's on the list.
The snake is a Ball Python, a snake from Africa that I doubt had never been seen in England in those times.