On the Wild Coast the summer storms come in off the sea in the afternoon, black-bellied and fast, and the lightning that falls out of them kills more people here than in most places on earth. When a bolt strikes a hut or a kraal or a person, the question is not only what happened but why here, and why this house. The tradition has an answer. Something landed.

The impundulu, the lightning bird, is a creature of the Xhosa, Mpondo and Zulu worlds, and the eastern seaboard is where it is most spoken of. It is described as a bird the size of a person, black and white, with the beak and talons of a raptor. Lightning is what it does: the flash is the bird coming down, the thunder is its wings, and the scorched patch on the ground is where its feet touched. Some say it lays an egg where it strikes, buried in the earth, and that the egg has to be found and dug out and dealt with, or the place will draw lightning again.

It has another side, which is the one that frightens people. The impundulu can take a human shape, usually a handsome young man, and in that form it seduces women. It drinks blood, in some tellings from cattle and in others from people, and it is never satisfied. Above all it can be owned. A witch, in the tradition almost always a woman, keeps an impundulu as a familiar and passes it down to her daughter. Sent against an enemy, it brings wasting sickness, madness, sudden death. It cannot be shot, stabbed, poisoned or drowned. Fire is the one thing it fears.

Which is why the people who deal with it are specialists. Zulu heaven-herds, the doctors of the sky, would go to the site of a strike to search the ground for the bird, or for its droppings and fat, and the fat was boiled up with medicines into an ointment against lightning. Xhosa diviners would be called to a house that had been struck to say whether the bird had come on its own or been sent, and by whom. Some traditions connect the bird with the hamerkop, the odd brown wader with the hammer-shaped head that builds enormous nests beside rivers; to harm one is to invite the lightning.

The earliest written account we have found is from 1870, when the missionary Henry Callaway, writing down what his Zulu informants told him, recorded the inyoni yezulu, the bird of heaven, that the heaven-herds hunted after a strike. That is why this entry sits at 1870 on the timeline. The tradition is a great deal older than the man who first put it in a book.

It is also not a museum piece. In 2005 a South African court convicted a man of culpable homicide after he killed a small child he believed to be an impundulu in disguise. Diviners are still consulted after strikes. Lightning still kills more than a hundred South Africans in a typical year, a great many of them along this coast.

Here is what the tradition and the physics agree on: lightning comes down, it chooses a place, and it leaves a mark. Where they part company is over what, if anything, was riding it.