A paedophile blackmailed young internet victims into extreme and degrading sexual and physical acts, forcing one to lick toilet seats and eat dog food.
Cambridge graduate "highly manipulative" Matthew Falder made children, young men and women photograph themselves in compromising positions, sharing the material online with other paedophiles on the so-called dark web.
Prosecutors described how he targeted vulnerable people, including anorexic teenagers, posing on the internet as a depressed female artist offering them money for images.
He contacted 300 people in this way through their online advertisements on sites like Gumtree but if they agreed, "predatory, serial offender" Falder would blackmail them with a "constant stream" of increasingly depraved requests.
One young girl was forced to take naked video and pictures of herself holding signs with racist and homophobic slogans, messages to other paedophiles, and to lick a used tampon.
Opening the case at Birmingham Crown Court on Wednesday, Ruona Iguyovwe said he enticed his victims "to produce increasingly severe self-generated indecent images of themselves, the focus of these images being to humiliate and degrade the victims".
Falder, 30, of Edgbaston, Birmingham, was only snared after an investigation led by the National Crime Agency (NCA) and help from GCHQ, along with international cooperation from the FBI, and law enforcement in Israel, Slovenia, Australia and New Zealand.
He had previously admitted 137 charges against 48 victims, in offending stretching over eight years, until 2017.
Ms Iguyovwe said once the former Birmingham University geophysicist researcher had compromising images of his victims, he offered a choice; either they send him more material or he would send the images to their friends and family.
He told one to "choose carefully", or he would "send the images to everyone on Facebook associated with your school, and in letters to your parents and teachers, explaining with printouts of all the pictures that you will strip for money".
Three of his victims attempted suicide.
But "unmoved" Falder, who hid behind pseudonyms and online personas like "666devil" and "evilmind", was interested only in more images, telling one youngster "you must send enough good ones for me to be happy".
Controlling Falder, who never met his victims, encouraged another youth to rape a four-year-old boy.
He distributed the images on websites known to be associated with paedophiles and those interested in "hurtcore" - described as material which depicts rape and abuse.
When some victims threatened to tell parents or police, "sophisticated" Falder simply bragged "I can't be caught".
He used anonymous email accounts and online connection software Tor, to cover his tracks.
Falder, who also quizzed victims for personal details, and scoured their Facebook pages, gained the confidence of others by sending naked images extracted from previous victims, and pretending they were him.
Describing the impact of Falder's actions, one of his victims told the court: "I feel dirty, like used goods."
In an emotional statement, the victim added the ordeal had triggered the breakdown of relationships with her parents and boyfriend, and forced her to leave home.
"Part of me believes that's all I am good for anymore - to be abused," she said.
Judge Philip Parker QC told her she was "exceedingly brave" for coming to court.
The three-day sentencing hearing continues.