"He accepts he was a determined and committed pedophile," the prosecution said of Ian Watkins.
According to the BBC, the 36-year-old Welsh musician pleaded guilty to "three counts of sexual assault involving children and six involving taking, making or possessing indecent images of children and one of possessing an extreme pornographic image involving a sex act on an animal."
Court documents show Watkins had recorded his crimes and kept the evidence on his computer.
Police say some of the material recovered was "too extreme" to detail.
In addition to Watkins, the prosecution also brought charges against two female co-defendants who "abused their own children and made them available to Watkins for him to abuse."
One of the two women was the mother of an 11-month-old boy whom Watkins admitted he attempted to rape.
"This investigation has uncovered the most shocking and harrowing child abuse evidence I have ever seen," South Wales Police rep Peter Doyle said. "There is no doubt in my mind that Ian Watkins exploited his celebrity status in order to abuse young children."
The prosecution said drugs played "a significant part in his offending against children."
Watkins initially denied the charges against him, claiming he was the victim of a "malicious campaign."