Growling from around a corner precedes the arrival of a menacing ghoulish figure with skull-like face, hideous teeth, cascading hair, oddly tasselled gloves, and an inside-out sheepskin gown tied by a broad leather belt that should be around the neck of a cow, the bell projecting to one side. Luckily, this is only a miniature Tschäggätta: a late-afternoon returnee from school looking to get some scaring in before dinner. It is easily placated.

After dark things will get more hairy. Groups of growling monsters twice the size will roam the streets in small bands, intimidating passers-by and entering Kippel’s cosy Dorfkeller and Hotel Petersgrat restaurants to dismay diners enjoying hearty cheese-laden dishes.

The first written record of the Tschäg­gättä dates to 1599, and mentions horrible figures descending the valley to protest excessive taxes and tithes. This makes their annual reappearance, between the festivals of Candlemas (February 2) and midnight on Shrove Tuesday (a movable feast – this year, February 16), perhaps Switzerland’s oldest carnival, as well as something unique to the Lötschental.

This long, narrow valley in the Valais Alps is less developed than its neighbours, never having received a railway line and not even a decent road until after World War II, although trains from Geneva, Lausanne and Montreux now climb as far as Gampel-Steg, where there’s a connecting bus service.

Between them, the valley’s four villages can muster a population of only 1,500, their dialect obscure even to other Swiss-German speakers. Almost everyone, male or female, has been a Tschäggätta at some time. Groups of friends, young and old, collect around a mask carver such as 26-year-old Michael Ebiner, who inherited his position and a large collection of masks from his uncle when he was only 14, and who has been terrorising every year since he was four.

The winter before last, in a secret cellar lined with masks and racks of costumes and to which only his friends are usually admitted, Ebiner showed me how elaborate padded frames raise shoulders and distort body shapes. The whole costume, with its multiple layers and large cowbell, is heavy even before the cumbersome wooden mask is donned. As Ebiner and his friends demonstrated, Tschäggättä may need two assistants to help them dress.

Legs and even boots are wrapped in hessian sacking to ensure anonymity. The event is entirely in fun but some may use it to settle scores, with a little jostling, a deluge of snow in the hair, or tasselled gloves rubbed in the face – although not this year, as coronavirus-forced social distancing will be maintained.

“When I see someone coming,” said Ebiner, of the times when he’s not out menacing himself, “I put my glasses on the table so they don’t get broken, and just wait for it.”

He had a rack of lesser masks for loan to seasonal supplicants without their own, but the best were reserved for his closest friends, some now living away in Zürich or Luzern but who return for the festival.

“During the carnival we get together every day and have a good time,” said Ebiner. “That’s most important: it’s a reunion.”

The procession of Tschäggättä from Blatten to Ferden that opens the season may have been cancelled this year, as has the Lötschental Carnival of local traditions that ends it, but the fun is mostly to be had in between.

The Tschäggättä have no committee or organisers, and little in the way of rules for their marauding. This is no made-for-tourists event but one that the Lötschentalers make for their own amusement.

There will be common-sense conformity with health regulations this year but the local authorities were wise to open their newly published Carnival Code by stating that it “is in no way intended to constitute prohibitions”. Attempts to prohibit the Tschäggättä have never gone well.

In the 19th century, the frolicking had become genuinely frightening and occasionally violent, and the all-powerful Catholic Church, disliking this pagan pastime, banned it. To its shock, the Church found that although mask-making was suppressed in Kippel in the 1890s, the practice carried on uphill, in Blatten. Eventually a compromise was reached: no marauding after dark, never on a Sunday, and everything to be finished by Ash Wednesday.

Some say the festival began as a way of chasing winter away, or scaring off demons, but Ruth Rieder-Imseng, whose family has done much to keep the tradition alive, said that more likely it was born of practicality. Those living on the more shadowed and less productive side of the valley may have run out of food midwinter and donned hideous disguises to steal supplies from those living on the sunnier side.

Rieder-Imseng provides a year-round education in mask-carving and Tschäggättä history in a creaking old house called Zur Blauen Stube, in the village of Wiler. Her extensive displays include many ancient masks and a variety of costumes, some simple to put on or take off, but older ones far more complicated. “It takes three hours to get dressed, because the parts are sewn together and just the sides are open, and there’s the hole for the bell,” she said. “In [some] you can’t sit down. You can’t go to the toilet. Nothing.”

While traditional carvers see a mask shape hidden in a block of wood, and work to reveal it, some novices take ideas from Hollywood monsters, including those of Alien creator and fellow countryman H.R. Giger, and paint them in gaudy acrylics. And even keeper of tradition Rieder-Imseng approved: “Modern and traditional; they mix it very well.”

Carver Albert Ebener, 72, a retired bus driver who learned mask-making from his grandfather, makes 10 masks a year in a chisel-strewn little workshop in Kippel, but only on commission for those he knows. They are carved from local Swiss stone pine, and the rear covering and cascade of hair are of mountain goat. Smaller decorative masks and other trinkets are made for sale as souvenirs, but no mask-maker sells proper masks to outsiders, and their ownership is a secret.

“This is for a woman,” said Ebener, in 2019, holding up a mask he was repairing. “The teeth are cows’ teeth. It’s an old one – 60 or 70 years.” But that’s all he was going to say.

In the 1980s, the head of the valley’s council, the Talrat, again decided that Tschäggättä activity should cease, and declined to hear petitions to the contrary. And again authority was ignored. Instead, Tschäggättä numbers increased, with not only young bachelors taking part, but now women and children, too. And regardless of the agreement with the Church, most activity again takes place in the evenings – because few people are free in the daytime.

This year, the groups will be smaller, there’ll be no switching costumes, and no direct contact with those harassed. But the Tschäggättä will be stalking the Lötschental as usual.

“Some say the origin of the Tschäg­gättä was to drive away evil spirits,” explains Lukas Ebener, the leader of one Blatten group. “This year, we will try to drive away the coronavirus.”