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Perched on a throne adorned with cattle horns, the voodoo priest warns the housewife knelt in front of him of the deadly consequences of defying his powers.
'If you cheat on your husband, you will suffer for it, both you and the man you cheat with,' he says, wagging a gnarled finger. 'Defy the shrine and it will come and kill you.'
Just in case she has any doubts, High Priest Godspower Ojoduma shows her an photo album full of corpses, their limbs twisted and stomachs grotesquely bloated.
'You see them?' he says. 'That one was a witch, that one a thief, that one a liar. All sinners. All dead.'
This bloodthirsty ceremony, witnessed by MailOnline, is an oath-taking ritual for the ancient slave god Ayelala, one of the most feared of all Nigeria's voodoo or 'ju-ju' deities.
For hundreds of years, her potent magic has been used to enforce everything from debt collection and land disputes through to marital infidelity.
But in the 21st century, she has acquired a chilling new role in a very modern social problem - the trafficking of sex slaves to Britain and Europe.
As the ruthless trade has escalated in the past decade, Nigerian trafficking gangs have begun evoking Ayelala's powers to terrify local women into doing their bidding.
The gangs bring thousands of young Nigerians into Europe every year, luring them promises of jobs in shops or hair salons, then forcing them into prostitution when they arrive.
To ensure they do not run away, they make them swear oaths to Ayelala before they leave Nigeria, often forcing them to provide clippings from their pubic hair as an 'offering'.
Such is the fear that voodoo inspires that many of the victims prefer to remain in sex slavery rather than disobey.
To see the sex trade's sinister alliance with black magic first hand, MailOnline travelled to poverty-stricken Benin City in southern Nigeria, home to an ancient African kingdom where voodoo priests are still widely revered.
West Africa was once also the major market for transatlantic slaves and today, in a chilling echo of that role, Benin City has become the main hub for trafficking African prostitutes to the streets of London, Rome and Paris.
Such is the scale of the problem that local anti-trafficking charities believe that most young women will be approached at some point by a trafficker.
While most end up in Italy, because of its proximity to the Mediterranean smuggling routes, hundreds also find their way every year to Britain - home to Europe's largest Nigerian diaspora.
At Mr Ojoduma's temple in Benin City last week, MailOnline watched him perform a fidelity ritual on a housewife whose husband had taken her there on suspicion of having an affair.
Despite the gory threats he issued, Mr Ojoduma insists that Ayelala's oaths are never used for evil purposes.
But Osas Omaghomi, 27, told of how she was lured to Italy by a Benin City 'madam' who paid the €1,000 fee for a people-smuggler to take her across the Sahara and the Mediterranean.
Before she went, however, the madam took her to a shrine dedicated to 'Shango', a voodoo Thunder God.
'Before I went on the journey I was taken to a shrine with three other women,' Osas said.
'A lady trafficker made us cut clippings from our fingernails and hair and put them on top of the shrine, and we lay down in front of it.
'We were also made to drink a glass of schnapps and rub white powder in our faces, so that nothing bad would happen to us before we reached Italy.
'Then we had to swear at the shrine before Shango. We were told that if we didn't pay back the money we owed the madam, Shango would come and kill us by sickness.'
'I was terrified that Shango would come and get me, but I met a local pastor who reassured me and brought me home.'
Joan, a Nigerian woman who was trafficked at 17 and deported from Italy at 22, told of her ritual at the hands of a ju-ju priest.
'He cut off my hair, my armpit, my private parts, my nose...then he took my picture,' she said.
|A Bini hut used for some of these rituals|
'Sometimes people do come and ask, but I always turn them down. There are plenty who bring Ayelala's name into disrepute, but I have nothing to do with them.'