The man kept calling back, first from the same line, then from a series of new numbers.

“I got really scared,” Mr. Adomako, 21, recalled recently. “Nana is a famous fetish priest in Ghana. I thought he might want to put a curse on me.”

His fear was understandable. Mr. Kwaku Bonsam is a major figure in his home country, a traditional priest loved and despised for his spiritual powers. And he revels in his notoriety. “Bonsam,” a name he gave himself, means “devil” in the Twi language.

But in New York this spring, the devil just wanted to buy an advertisement. And so after listening to his voice mail, Mr. Adomako, who immigrated from Ghana six years ago, invited him by the offices of ZenoRadio, the online start-up where he works.

In place of the Ghanaian smock and kufi hat worn by most traditional priests, Mr. Kwaku Bonsam, 39, arrived in a shiny black Dolce & Gabbana tracksuit and a knit cap with “New York” woven in graffiti-style letters. His face was a mask of scar tissue from a near-fatal accident in his youth.

He had come to the city last year to visit a friend from Guinea, he said. But he extended his stay after his facial injuries became infected, requiring a number of operations at Harlem Hospital Center. “I love New York,” Mr. Kwaku Bonsam said in his newly improved English. “But it is too cold here.” He was planning to leave in August, a year after he arrived.

Back in Ghana, he has 14 children (9 of them adopted) and a religious empire: a network of shrines, a free elementary school, houses, cars and a cattle farm. He regularly appeared on television talk shows and could rally crowds of thousands.

Renowned as a healer, Mr. Kwaku Bonsam claims to treat everything from curses to impotence. But he is best known for his ambitious efforts to modernize the indigenous West African religion dominant before Christian missionaries began arriving in great numbers in the mid-19th century.

So why was Ghana’s most feared fetish priest living inconspicuously in a one-bedroom apartment in the Bronx?

In West Africa, traditional priests — often called fetish priests — have historically preferred secrecy and seclusion, carrying out their ancient rituals inside mud huts in remote areas. And since 1992, when a democratic constitution was approved in Ghana, traditional religion has come under increasing attack from a new generation of Pentecostal pastors, who use television, radio and the Internet to deride its rituals as devil worship.

In a clever reversal, Mr. Kwaku Bonsam has adopted these same platforms to promote traditional religion. His outsize public persona and his cosmopolitan credentials make the case that the old spiritual practices are compatible with being a modern African.

“In Africa, traditional religion has always been considered extremely local, while Christianity was seen as a way of joining the larger world,” said Birgit Meyer, a professor of religious studies at Utrecht University in the Netherlands who conducted research in Ghana for 25 years and has written about Mr. Kwaku Bonsam. “But by using Facebook and YouTube and finally residing in New York City, Mr. Kwaku Bonsam shows that traditional religion can also go global. He’s making it fashionable, in other words.”

New York was a natural destination for Mr. Kwaku Bonsam. Ghanaians make up the largest African immigrant group in the city, with a population of around 24,000, according to the Census Bureau. The majority of these hail from the Ashanti region in southern Ghana, where Mr. Kwaku Bonsam was born and is still based.

“He’s everywhere in the Bronx right now,” said Daniella Asantewaa, 25, a Ghanaian who lives in the borough and works in advertising. “You go to a funeral, you see him; a birthday party, he’s there.”

And yet many Ghanaians in New York view Mr. Kwaku Bonsam with distrust, if not outright contempt.

“According to my understanding, he’s an advocate of the devil,” said Ms. Asantewaa, who belongs to a Pentecostal church. “He’s someone I try to avoid.”

Hundreds of her countrymen, along with immigrants from West African countries like Ivory Coast and Senegal, have nevertheless sought out Mr. Kwaku Bonsam. On a recent Sunday morning, a dozen visitors were packed in his living room.

In one corner, a glass coffee table was obscured beneath the elements of a makeshift shrine: a chalice filled with Johnson’s Baby Powder, a bottle of J. H. Henkes’ Aromatic Schiedam Schnapps, a horsetail whip, a Master Lock wrapped in red twine. In another, an Ikea desk supported two Dell computer monitors and a broadcast microphone. In the middle sat Mr. Kwaku Bonsam, dressed in a rainbow-colored smock and stirring a brown liquid in a plastic kitchen bowl.

“This is Africa medicine,” he said, describing the concoction — prescribed to male clients experiencing “sexual weakness” — as a mixture of honey, vodka, tree bark and herbs he had requested from his assistants in Ghana. “Western medicine has a lot of side effects. But with this, there are no side effects.”

Daniel Nyarko and Kito Aikins, cabdrivers in their early 50s who had moved to the Bronx around 30 years ago, were sitting nearby.

“We came to America for Martin Luther King’s dream,” Mr. Nyarko said, eliciting knowing laughter from the others in the room. “But New York is very, very expensive. There is so much stress here.”

Mr. Aikins added: “Nana helps people spiritually in ways that pastors cannot.”

Now and then, a Skype call came through on Mr. Kwaku Bonsam’s MacBook Pro. One caller — Lewis Lidfeldt, a 20-year-old Ghanaian living in Sweden — was seeking advice on how to become a successful recording artist. “I heard Nana has a lot of experience with the spirit,” Mr. Lidfeldt said. Mr. Kwaku Bonsam asked him to call back later.

Among the visitors that morning was Nana Acheampong-Tieku, the regional chief of the Ashanti people in New York. An accountant by day, he explained that Mr. Kwaku Bonsam’s local popularity had frustrated Christian pastors here.

“They think he’s stealing their members and their revenue,” Mr. Acheampong-Tieku said. He named a controversial Pentecostal pastor in Virginia who had openly criticized Mr. Kwaku Bonsam during his popular conference-call prayer service.

Mr. Kwaku Bonsam, who had been listening quietly, suddenly pounded his fist on the coffee table, raising a small cloud of baby powder.

“He should preach according to the Gospel and stop insulting me!” he shouted in Twi. “Tell him to read Jeremiah 23:16.” The biblical passage admonishes: “Do not listen to what prophets are prophesying to you; they will fill you with false hopes.”

The Ghanaian news media treat Mr. Kwaku Bonsam as a celebrity and have chronicled his sometimes rocky relationship with his third wife, Gertrude, a law school student in London.

“Kweku Bonsam Suffering From Broken Heart,” the Web site Peace FM Online reported in 2012, after learning of a disagreement between the couple. A year later, after she visited her husband in the Bronx, the Web site Ghana Nation ran the headline: “Ghanaian Fetish Priest Kweku Bonsam Chills With Lover in New York.”

Before he was Nana Kwaku Bonsam, though, he was Stephen Osei Mensah, a member of the Seventh-day Adventist Church in the small village of Afrancho.

The transformation began one night in 1992, when he was 19. While carrying a lantern near his home, he accidentally walked into the path of an open gas line. The flame triggered an explosion. Mr. Kwaku Bonsam barely survived. He was released from the hospital with extensive burn scars on his face and torso. Ostracized for his appearance, he dropped out of school and found work as a mechanic in the Suame Magazine, a bustling industrial district outside Kumasi, the regional capital.

In his mythic origin story, Mr. Kwaku Bonsam claims to have received his supernatural powers after he saved a sick man’s life on his way home from work one day. In return, the man gave him a “mysterious gift,” a kind of braided horsetail, that enabled him to help other people.

Soon after, Mr. Kwaku Bonsam opened a small shrine room in his mother’s house in Afrancho. Before long he had generated enough revenue through consultation fees to build a large shrine complex nearby. It was around this time that he took the last name Bonsam as a taunting response to the Pentecostal movement’s continuing demonization of traditional religion.

In Ghana, 71.2 percent of the country’s 25 million people identify as Christian, while only 5.2 percent say they believe in traditional religion, according to a 2010 census report. But Kwabena Asamoah-Gyadu, a professor of African Christianity at Trinity Theological Seminary in Accra, Ghana’s capital, said that those numbers should be read loosely.

“In African culture, when people experience a crisis, they often put their Christian beliefs aside and consult traditional priests,” he said. “They won’t usually admit it, of course, because that destroys their Christian credibility.”

It was a similar situation that made Mr. Kwaku Bonsam famous, said Frederik Lamote, a professor at University College Brussels who wrote part of his doctoral thesis on him.

On April 2, 2008, Mr. Kwaku Bonsam stormed into the church of Collins Agyei Yeboah, a popular Pentecostal pastor in Kato, another southern town. Accompanied by a crew of policemen and reporters, he accused Pastor Yeboah of secretly soliciting the help of his traditional gods and then failing to properly compensate him and the gods for their services. Mr. Kwaku Bonsam claimed the gods had given him two choices: to retrieve the idol he had given the pastor, or to die at 6 p.m. that day. “Do you want the gods to kill me?” he asked Pastor Yeboah.

In YouTube videos of the episode, viewed hundreds of thousands of times, Mr. Kwaku Bonsam went on to say that 1,600 pastors from around the country had visited him requesting juju spirits to help build their churches. The idol is eventually retrieved from behind Pastor Yeboah’s church and after a lengthy interrogation, the pastor is led away by the police. In the video, he angrily defended himself by saying that he had indeed consulted Mr. Kwaku Bonsam, but that the powers he had given him didn’t work.

The success of Pentecostalism in West Africa, with its exorcisms and speaking in tongues, depends heavily on its resonance with traditional religion. But by showing that a well-known pastor had explicitly relied on juju spirits, said Professor Meyer, Mr. Kwaku Bonsam “affirmed widespread rumors that pastors had secret spiritual resources.” His popularity soared in response.

Today, his sprawling shrine complex in Afrancho, with 18 guest rooms, attracts people from all over the world, who pay a fairly hefty price — 10 Ghanaian cedis, or around $5 — to see him. But the bulk of his earnings, Professor Asamoah-Gyadu said, come from wealthy businessmen and politicians in the form of donations and “gratitude money.” It is this, he added, that allows Mr. Kwaku Bonsam to provide free tuition for over 1,000 schoolchildren in Afrancho, for instance, as well as to afford skin graft operations at Harlem Hospital.

Pentecostal pastors in Ghana, perhaps envious of his success, regularly challenge him to spiritual battles to prove who possesses greater powers.

In one memorable showdown, Mr. Kwaku Bonsam, exhibiting his trademark flair, rode into Jubilee Park in Kumasi on a horse, adorned in traditional battle dress. The event was broadcast on the radio. Thousands came out to watch.

The pastor never showed up. In celebration, the newspaper Daily Guide reported, Mr. Kwaku Bonsam conjured live birds and money in different denominations, prompting a small riot. The police fired tear gas into the crowd to disperse it.

Life in New York has, by comparison, been fairly uneventful. With little space and no work permit, Mr. Kwaku Bonsam has been unable to perform the highly elaborate rituals he is known for in Ghana, in which he claims to become possessed by spirits, conducts animal sacrifices and throws gunpowder onto open flames.

To Mr. Acheampong-Tieku’s knowledge, Mr. Kwaku Bonsam has become possessed only once in the Bronx. “He started speaking in a spirit language,” recalled the Ashanti chief, who was in Mr. Kwaku Bonsam’s apartment with several others. “He showed what things are going to happen, and told a few people what they could do for themselves, like what not to eat.”

“It was pretty calm,” he added.

Still, Mr. Kwaku Bonsam has made his way into all aspects of Ghanaian life here. He has improved his English and become fluent in the rhythms of life in a global capital.

Appearing in traditional robes, he takes part in monthly meetings of the Asanteman Association of the U.S.A., the Ashanti cultural group over which Mr. Acheampong-Tieku presides. He has also participated in ceremonies held by the local Akan community, an ethnic group native to Ghana and Ivory Coast.

He is equally at ease at secular functions. Dressed rakishly in a dark suit, he turned up in the front row of the Miss Ghana USA Pageant at the Alvin Ailey American Dance Theater in Manhattan on June 28.

David Quansah, a suave TV and radio presenter in Ghana known as Papa Sly, was a host of the event, which drew around 250 people, most of them Ghanaians. Seeing Mr. Kwaku Bonsam in the crowd, he asked everyone to acknowledge “the presence of a very special guest,” leading him to stand and wave. Several people gasped before applause drowned them out.

A few days earlier, the pageant contestants were relaxing in a Harlem town house. Primarily Christians, they questioned the motives of Mr. Kwaku Bonsam’s presence in New York.

“Fetish priests prey on the directionless and the vulnerable, those seeking any kind of answer,” said Adwoa Adofo, 28, a communications director in Washington.

“I read that he sat on an egg and it didn’t break,” said Nadia Asiedu-Baah, 19, a student at Concordia University Wisconsin. “But is there a video of this? Where’s the proof?”

During the pageant, however, Mr. Kwaku Bonsam quickly became part of the proceedings. Mr. Quansah asked him to present the awards for Miss Congeniality, People’s Choice and Most Photogenic, the last of which went to Lisa Aidoo, 19, a student at the Fashion Institute of Technology in Manhattan who was representing the Ashanti region.

“She is good,” Mr. Kwaku Bonsam whispered after sitting back down. “She will win, I think.”

When she placed second, Mr. Kwaku Bonsam clapped his hands to his forehead. “No, no, no!” he said.

The traditional priest has enjoyed his year in New York, but with his surgeries completed, he is also ready to leave. “People ask me on Facebook, ‘Nana, when do you come back to Ghana?’ ” he said in an earlier interview. “There are rumors back home that I am dead.” He said his departure was imminent: he had bought a ticket to Accra leaving on Aug. 15.

After the event, an exhausted Mr. Quansah, who had interviewed Mr. Kwaku Bonsam on several occasions in Ghana, confirmed the death rumors. “When he returns, we need to have another TV interview,” he said. “The public has to know he is very much alive.”A version of this article appeared in print on July 21, 2013, on page MB1 of the New York edition with the headline: A Visit From the Devil.

A version of this article appeared in print on July 21, 2013, on page MB1 of the New York edition with the headline: A Visit From the Devil.