William Kamm, also known as "Little Pebble", was the leader of the Order of Saint Charbel, a religious cult run from a NSW south coast property.
The 76-year-old saw himself as a pope, visionary and prophet who sent messages from Jesus Christ and the Virgin Mary to his followers.
He and his 60-year-old wife Sandra Susan Mathison faced a judge-alone trial at Sydney's Downing Centre District Court which commenced on Tuesday.
They have pleaded not guilty to jointly grooming the girl between 2010 and 2020 while she was aged between six and 16.
Kamm has also denied inciting the girl to commit an indecent act and twice breaching his extended supervision orders by contacting her.
The woman - who cannot be legally identified - said she understood she was to be Kamm's wife even when she was as young as six years old.
"His role was to try and get us to do God's will," she testified.
Crown prosecutor Andrew Norrie told the court Kamm ordered he have 12 wives, known as "queens", and other women referred to as "princesses" who were chosen by the Virgin Mary.
These women were on a "mission from God" to become impregnated and repopulate a new era of society after natural disasters destroyed the world, leaving Kamm and his followers behind, the court was told.
At first, the girl was not allowed to speak to the cult leader directly by phone as he was in jail but was instead referred to using code words, the prosecutor told the court.
"Hi, my darling, I can't wait to see you to start this beautiful mission together," Kamm allegedly said during a call to the girl when she was six.
When she was seven, she agreed to be "spiritually married" to Kamm, Mr Norrie said.
Mathison allegedly said she could not be with other boys and she had to keep her "marriage" with Kamm a secret as the devil would try to stop it.
During a call in October 2013, the cult leader allegedly said the then nine-year-old should put on her running shoes so he could chase her.
It's alleged he also said he wanted to lock her in a closet to keep her for himself.
When the girl told Mathison she was uncomfortable, she was allegedly told Kamm did not have any dirty thoughts and he was only doing God's will.
The pair also made plans to take the girl on an international cruise once he was released from jail as there were no age of consent laws there, Mr Norrie said.
Kamm was released on parole in November 2014 and placed under supervision orders that barred him from contacting females aged under 17.
He allegedly breached this order by talking to the girl over the phone.
When she was aged 15 in December 2019, it's alleged the complainant received a letter from Kamm saying Jesus predicted she would have 45 children.
In March 2020 during a stay at the Order's property, Mathison allegedly told her she could receive Kamm's sperm in a cup to impregnate herself.
Around that time, plans for her to meet the religious leader in person for the first time were put on hold as Australia went into lockdown during the COVID-19 pandemic.
Kamm and Mathison were arrested in September 2024.
The cult leader's barrister David Mulligan gave brief submissions saying his client had never physically met the complainant.
Barrister Dev Bhutani, representing Mathison, attacked the crown case against his client saying it was "derivative" of the case against Kamm.
The trial continues on Wednesday.
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