A Reynoldsburg man who persuaded a teen-age girl to become his sex slave will be prison-bound for the next 25 years.

A judge sentenced Donald M. Cosstephens, 43, yesterday to serve the entire term behind bars with no chance of parole.

Cosstephens pleaded guilty yesterday to 50 felony sex offenses, including having unlawful sexual conduct with the 15-year-old South Carolina girl.

According to a master-slave contract the two signed, he owned the girl's body, investigators said. Cosstephens told investigators that he had sex with her last June when he brought her to Ohio.

Among more than 10,000 images Cosstephens helped investigators locate on his computer were various images of the girl self-mutilating her sexual organs at his direction.

Other images showed nude children ranging from about 9 months to 16 years old, engaged in sex with other children and adults.

Assistant Franklin County Prosecutor Ron Welch said he was not concerned that Cosstephens get help in prison but that "another girl will not have to deal with him for another 25 years.''

Cosstephens, who went by "The Coss'' on the Internet, met the girl via a sexual-fetish chat room and persuaded her to come to Reynoldsburg last year. He and his then-roommate, Janice E. Stanton, drove to the girl's home and posed as the parents of one of the girl's friends who had moved to Ohio. They drove her back to Reynoldsburg and kept her the month of June.

The girl's mother later found computer files that detailed the abusive relationship and called police. The Greenwood, S.C., police traced the correspondence to Cosstephens and notified Reynoldsburg police and the Ohio Bureau of Criminal Identification and Investigation.

The agencies searched Cosstephens' apartment at 7105 Shawnee Way in August. Welch filed 112 felony charges against him in December.

Cosstephens declined to speak at the hearing. He did not contest being found a sexual predator by Common Pleas Judge Alan C. Travis.

At the end of his prison term, Cosstephens would be 68. He would have to report to the county sheriff wherever he lives every three months for the rest of his life.

The South Carolina girl's family was not in court, but Welch had told it about the plea deal.

"They were very satisfied with the result and very satisfied their daughter would not have to testify,'' he said.

Police were still seeking Stanton, 46. She is charged with four counts of unlawful sexual conduct with a minor.