Nine people have made complaints against a former GAA official accused of sex abuse and voyeurism over 30 years, the High Court has heard.
Prosecutors claimed Thomas McKenna, 58, had stored more than 50,000 photos and video clips, many showing young men and boys naked or partially clothed.
Police are still working to establish the identities of some of those pictured, a judge was told.
In court in Belfast on Wednesday, Mr McKenna was refused bail.
The judge, Mr Justice McAlinden, said: "The allegations made against the applicant are of the most horrendous nature in terms of offending against young vulnerable children."
Mr McKenna, of Woodside Park, Bessbrook, County Armagh, faces 17 charges between 1988 and August 2018.
They include serious sexual offences against persons aged over 16 without consent and two gross indecency offences, one of which was against a child.
He is also charged with sexual assault, voyeurism and eight counts of indecent assault, as well as making and possessing indecent photographs of children.
The retired postman is also alleged to have interfered with mail during his time in his job.
A crown lawyer said the charges relate to a "serious and complex investigation" into claims of historical sexual offences.
"It involves, to date, nine injured parties," she told the court.
She said they had given police interviews and they claim Mr McKenna took photographs and videos of them without permission.
The court heard police searches led to the recovery of devices said to contain 43,000 still images and 8,000 short video clips - some allegedly taken covertly.
The prosecution said the haul included photos taken in more recent times.
Opposing bail, the prosecution said Mr McKenna had received a death threat.
A defence lawyer said his client had been merely advised of heightened tensions in Crossmaglen where he had served as treasurer for Crossmaglen Rangers for many years.
The club has issued a statement in which it assured members of its "robust child safeguarding procedures", and encouraged anyone with information about the investigation to co-operate with the authorities.
It confirmed Mr McKenna had been excluded from all activities pending the outcome of police inquiries.
Bail was refused. The judge pointed out that not all the alleged offences are historic.
"The court would be remiss in its duty to protect the public if bail was granted," he said.