She survived an ordeal beyond belief but just over a year since escaping the clutches of the man who raped and beat her over more than a decade, Michelle Knight says she has forgiven him and is a "strong and powerful" woman.

Since escaping her captor and tormentor Ariel Castro on 6 May 2013, Knight has since changed her name to Lily, and at a speaking engagement on Sunday she appeared upbeat and optimistic about her future as a free woman.

Knight, 33, admitted to the audience at Notre Dame-Cathedral Latin High School in Chandon, Ohio, that she had at first "hated" Castro, but after having therapy, she came to feel that what he did "hadn't been his fault".

"He had a disease," she said.

It was also therapy that got her to the place where she could refer to Castro by his name and not "that dude".

"I was able to say his name, Ariel Castro...I was able to forgive him," she said, reports Cleveland.com.

Knight revealed that during her captivity in his house, she "just thought of myself as a punching bag because that's all he did to me".

She also commented on his suicide just a month into his life sentence for abducting her and two other women held with her, Amanda Berry and Gina DeJesus. 

"I felt very appalled by it, but I understood it," she said.  "I don't condone what he did."

She also spoke about her approach to life now that she is free, saying it was an "honour" to help everybody she could.

"If you're getting abused don't wait, get help," she told the audience.

She went on to say her perspective was that "God put us on earth for one reason, to do his work".

Her faith and the role it played in helping her through 11 years of captivity and abuse at the hands of Castro are mentioned in her new book, Finding Me, which she signed copies of at the event.

She summed up her attitude, saying: "I'm a strong and powerful woman.  I say what I mean and I don't take any crap from anybody.

"The situation [he] put me in didn't define me. I choose to live a meaningful life."