Bishop Street courthouse in Derry
The man, who cannot be named in order to protect the identity of the victims, was sentenced to 16 years at Derry Crown Court.
The sex beast, who is from the Waterside area of the city, will be placed on the Sex Offenders Register indefinitely.
Detective Superintendent Lindsay Fisher said: “What this man did to his victims over a 12 year period plumbed the depths of depravity.
“They will undoubtedly be left with long lasting trauma after suffering years of horrific abuse.
“I want to recognise the strength and courage of each of the victims, now adults, for coming forward and assisting Police with our investigation to bring this abuser to justice.
“It takes huge courage to take that first step of reaching out and breaking the cycle of abuse.
“We encourage anyone who has been the victim of any form of sexual abuse to come forward to Police, no matter when the abuse occurred.
“Please be assured that we have specially trained Detectives in our dedicated Non-recent Child Abuse Team who will treat all victims with sensitivity and respect – at every stage of the process.
“If you have ever experienced any form of sexual abuse, please contact police on 101 or call 999 in an emergency.”