During his reign as heavyweight champion of the world, no one was more feared than Mike Tyson, who obliterated opponents with ruthless efficiency.
But all the while, the troubled superstar was at war with himself, battling an abusive voice in his battered head that led "Iron Mike" to the brink of suicide.
He said that all changed when he began taking psilocybin mushrooms, more commonly known as "magic mushrooms," and other similar consciousness-altering substances.
Now the boxing prodigy from Brooklyn is experiencing a career renaissance that he said is the result of psilocybin-powered mental and spiritual exploration.
"Everyone thought I was crazy, I bit this guy's ear off," an upbeat Tyson told Reuters, referring to his infamous 1997 fight against Evander Holyfield.
"I did all this stuff, and once I got introduced to the shrooms ... my whole life changed."
To be sure, many people have had negative experiences with psilocybin, which can cause disturbing hallucinations, anxiety and panic. Medical professionals studying them warn against self-medicating or using them outside of an approved medical framework.
But Tyson, who turns 55 next month, and impressed in his November exhibition bout against Roy Jones Jr, said he has never felt better.
"It's scary to even say that," said Tyson, who is also a cannabis entrepreneur and podcast host.
"To think where I was - almost suicidal - to this now. Isn't life a trip, man? It's amazing medicine, and people don't look at it from that perspective."
"I AM CURED"
Humans have been ingesting psychedelics since the earliest days and as stigmas slowly dissolve, it is beginning to be taken seriously as a psychiatric medicine.
There is still much to learn.
Enter former NHL enforcer Daniel Carcillo, who was nicknamed "Car Bomb" for his violent approach to the sport.
After 164 fights, thousands of hits and at least seven concussions, the two-time Stanley Cup champion was forced to retire in 2015 due to repeated head trauma.
Like Tyson, he was at war with himself and struggling to connect with his wife and young children after his retirement at age 30.
He said psilocybin helped him bridge that gap and the experience led him to found Wesana Health, a first-of-its-kind company dedicated to studying its ability to treat traumatic brain injury (TBI) in athletes, veterans and others.
Wesana recently entered into a clinical research project with the World Boxing Council (WBC) to examine the potential of psilocybin to help boost the brain health of boxers, and Carcillo says he is proof that it works.
"I am cured, for sure, of TBI and any related symptoms. 100%," Carcillo said.
"I do not suffer from slurred speech, headaches, head pressure, insomnia, impulse control issues, anxiety, depression or suicidal ideation," he said.
"I do not suffer from any of that (anymore)."
Carcillo and his team are hopeful psilocybin will become an FDA-approved drug to treat TBI.
OPEN TO THE WORLD
Tyson said he wants to spread word of the benefits of psilocybin as widely as possible, which is why he has partnered with Wesana.
"I believe this is good for the world," said Tyson, who said he thinks its use could also help create a more empathetic and just society.
"If you put 10 people in a room that don't like each other and give them some psychedelics, they'll be taking pictures with each other," he said.
"Put 10 people in a room who don't like each other and give them some liquor, and they'll be shooting everybody. That's real talk.
"(Wesana) was on the same level of thinking that I was. They wanted to share this with the world. This is very limited, us doing this in these small ceremonies.
"It needs to be open to the world."