Benn said he is returning to boxing at the age of 55 to gain "closure" after being tormented by drug abuse, depression and the death of his brother during his career.
The former world champion, who revealed he suffered suicidal thoughts before turning to Christianity just over 10 years ago, has announced a one-off fight with Sakio Bika on 23 November in Birmingham.
Benn has not fought professionally since 1996 but, having found peace, feels he has unfinished business due to previous problems outside the ring.
"This fight is all about me. It wasn't financial, it was always about closure that I wanted that I never had," said Benn at a press conference in London.
"I suffered with a lot of issues in my life from a young age, from 1972 when my brother died - the murder of my brother - which I carried through to my adult life.
"At the age of eight, I started smoking cigarettes to 41, I started doing ecstasy, smoking spliff all through my career, but suffered with depression.
"There's not one fight that I went through that I never suffered with. It was bugging me.
"I don't even think I was at my best, I don't know how I got that far to be inducted into the hall of fame and voted the best super-middleweight in history along with Joe Calzaghe by the WBC."
Nicknamed the 'Dark Destroyer', Benn claimed the WBO middleweight title in 1990 and held the WBC super-middleweight crown from 1992 until 1996.
His most recent bout, a challenge for Irishman Steve Collins' WBO super-middleweight belt, came almost 23 years ago and ended unsuccessfully following his retirement after six rounds.
"I was in a dark place for so many years. There was no joy," he said. "I was having suicidal thoughts, I didn't want to be where I was. I just want you to understand what I was going through.
"And then, in about 2008, I had an encounter with Jesus, That's when my life changed, truly changed. As soon as I had that encounter, no spliffing, no ecstasy, no women, absolutely nothing."
Benn has been advised against his surprise return by a host of leading names in the sport, including promoter Frank Warren and Billy Joe Saunders, the current holder of the WBO super-middleweight belt.
Eddie Hearn, meanwhile, has expressed concerns about the suitability of the match-up with former WBC super-middleweight champion Bika.
However, London-born Benn brushed off questions about his age and ability to compete as he believes he is in the best physical condition of his life and compared himself to Benjamin Button, the character created by F. Scott Fitzgerald who ages in reverse.
"I feel the time is right now. People may say, 'you're 55'. It's nothing to do with age," said Benn. "I'm fitter now than when I was world champion.
"It's not the 'Dark Destroyer' because everything synonymous with that name is not who I am. Now it's Nigel 'Benjamin Button' Benn - the older I get, the fitter I am.
"And I 100 per cent mean that. I am so fit. I am in good shape and I'm ready to rock 'n' roll."
The meeting with Cameroonian-Australian Bika will be licensed by the British and Irish Boxing Authority (BIBA), rather than the British Boxing Board of Control (BBBofC).
Professor Michael Graham, the BIBA's chief medical officer, said examinations show Benn to be in similar shape to other boxers, describing him as the world's "fittest 55-year-old boxer".
"The tests that we have done on Nigel Benn to date indicate that his physiological age is at least 15 years younger than his chronological age," said Graham.
"That's scientific blood tests, MRI scans, cognitive function, body fat etc.
"If you look at some of the other boxers who have been sanctioned by other sanctioning boards and provided licences, Nigel's certainly as fit, if not fitter, than most of them.
"Certainly the fittest 55-year-old boxer on the planet."
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