A well-known beast in Irish legend is the Black Pig. How the legend started, it is impossible to say. Across the southern borders of Ulster lies a discontinuous earthwork. This, it is conjectured, was constructed in the Iron Age for defensive purposes. It is known as the Black Pig's Dyke.
The legend has a number of variants. In one, a schoolmaster who went in for magic as a sideline turned all the children in his class into hares, save one, which he transformed into a hound. The hound killed one of the hares. The child's mother was none too pleased with this development. She had magical abilities herself. She changed the schoolmaster into the Black Pig. Hunters chased the brute across the southern borders of Ulster and its trotters churned up the earthworks. The hunters finally killed it in County Sligo.
Another version has the father of a child grow concerned about his son's loss of weight. The unhappy boy told him that the schoolmaster had a magic book, which he used to change the boy into a hare and his schoolmates into hounds, which would then pursue him, presumably with luncheon in mind. The father suspected this was not part of the school curriculum and went up next day to confront the sorcerous pedagogue.
"Is it true," he asked, "that you have a book that gives you the power to change people into animals?"
"Indeed it is," admitted the schoolmaster.
"Well, now, isn't that the wonderful thing!" the father said. "Could you show me how it's done."
The obliging schoolmaster turned himself into a Black Pig. When he did this, the father flung the book into the fire and it was burned to ashes, much to the Black Pig's distress. In fact, when that worthy realized he was now in porcine form for ever more, his mind could could not withstand the horror. He tore across the countryside, his hooves throwing up the earth which formed the earthwork and, when he reached the Atlantic he either threw himself in and drowned or turned to one side and made off into the distance.
The Black Pig was no ordinary pig. He was a fierce looking creature and in one version he had a horn on his nose, like a rhinoceros.
Behind the legend of the Black Pig there may lie a more mythical figure, for it is believed that there will be a terrible battle in a place called the Valley of the Black Pig, where the Irish will at last defeat all their enemies. The Pig may have been connected with some kind of eschatological myth, of the same kind as the Ragnarok of the Norse.