The Richtersveld is the driest, emptiest, most beautiful corner of South Africa, a mountain desert wedged into the last bend of the Orange River before the sea. There are people who live there, the Nama stock farmers who have kept goats on it for centuries, and there are people who pass through, which for the last hundred years has mostly meant men looking for diamonds. Both groups will tell you about the Grootslang, and they tell it a little differently.

The name is Afrikaans and means big snake, which undersells it. In the story the diggers brought out, it is a serpent twelve to fifteen metres long, thick as a man, leaving a track a metre wide in the sand, with a great blunt head and, in some tellings, a diamond in each eye socket. It lives in a cave known as the Wonder Hole or the Bottomless Pit, somewhere in the mountains near the river, which drops straight down for twenty metres and then slopes away into passages nobody has followed to the end. The cave is said to run all the way to the sea, sixty kilometres off, or in another version to open into the bed of the Orange itself, so that diamonds are funnelled down it into the river gravels. The Grootslang lies on that hoard. It is greedy and cunning, and it has been known to let a captive go in exchange for gems.

The older layer, the one that belongs to the region rather than to the prospectors, is a creation story. When the world was new, it says, the gods made the Grootslang first and made it too well: too strong, too clever, too hungry. Realising the mistake, they split every Grootslang into two creatures, and that is where elephants and pythons come from. One escaped whole, and it went to ground in the Richtersveld. That is why modern drawings give it tusks and a trunk on a serpent’s body, though the diggers’ version was simply an enormous snake.

The story most often attached to it is Peter Grayson’s. He was an English businessman who came to the Richtersveld in 1917 with a party to look for treasure, on the strength of a rumour about stones that shone like fire in a cave. Lions attacked the camp and injured several of his men, who withdrew. Grayson went on alone and was never seen again. The diggers said the Grootslang had him. The lions, it should be noted, had already been introduced to the story.

Writers took it from there. Fred Cornell, a prospector who had worked the river, put the Wonder Hole into his 1920 book The Glamour of Prospecting, and Lawrence Green, who collected every strange tale the Cape had to offer, gave the Grootslang a good airing in the 1930s. Those are the earliest written accounts we have found, which is why the timeline puts this entry at 1920. The tradition itself is older than any of them, and nobody in the Richtersveld needed a book to hear it.

A later party did go down the Wonder Hole looking for the fire-stones. They found bat droppings, a great deal of them, and came up. The diamonds, of course, are real: the lower Orange and the coast below it have produced them for a century. Something has been guarding them. The mining companies would say it was them.