On social media, "Jessica" encouraged others to film themselves sexually assaulting their own children or family members and to send her the images.
Elstob fooled people into doing this in Australia, New Zealand and the US.
He told one American boy, "I love incest so much. You and your sister are playing for me.
"I love it and I love you. I'm going to ask my mum if we can move to where you are."
The boy was later prosecuted for abusing his younger sister.
"Do I get to see pictures of your kids tonight?" Elstob asked one New Zealand man who obeyed Elstob's detailed instructions to violate his own children in front of a webcam.
Elstob and the man discussed the father drugging his children.
He also convinced an 18-year-old Australian man to abuse his two-year-old niece.
Police found 4635 files of pornography on 10 of Elstob's devices.
A massive 600 of the images or footage were in the worst two categories for child abuse material.
Australian Federal Police and Victorian police discovered Elstob while investigating other child-exploitation cases.
After his arrest, Elstob told police he was relieved to have been caught, saying the images of the two-year-old girl repulsed him, but admitting he also enjoyed seeing them.
The Melbourne County Court heard that when Elstob was informed that one victim he was in contact with was a 10-year-old boy, he replied that he didn't care.
Elstob posed as "Jessica" or other women to manipulate others for four years, between March 2014 and March last year.
From his multiple electronic devices in the southeastern Melbourne suburb of Somerville, he convinced targets to perform sex acts on 11 child victims.
Prosecutors told Melbourne County Court that under Elstob's coercion, another 34 people, mostly children, sent him pornographic images.
Elstob pleaded guilty to 30 charges including encouraging sexual penetration of a child under 12, procuring a person under 16 to engage in sexual activity outside Australia, and child pornography.
Judge Gavan Meredith said Elstob had built an online world for himself, impersonating females online to manipulate people.
The court heard Elstob was a lonely, isolated man who was bullied and after revealing he was gay he left school in Year 11.
A psychologist diagnosed Elstob with pedophilic disorder and depression.
Judge Meredith said Elstob's mother remained supportive and the offender was keen to undergo rehabilitation.
But Elstob's child exploitation has caused enormous damage, and potential prosecution of the adults Elstob convinced to sexually assault children.
"Your offending is serious, calculated, deceptive and manipulative," Judge Meredith said.
"Aspects of the conduct which you encouraged were particularly grave, corrupting, and depraved."
He jailed Elstob for a maximum 12 years, which taking into account time in custody would mean Elstob must serve a further nine years until he is eligible for parole.
