When the radio D.J. Prince Adomako received a call in April from a man identifying himself as Nana Kwaku Bonsam, he hung up immediately, terrified. 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.