Toad venom or 5-MeO-DMT is an extremely potent natural psychedelic that comes from a rare species of toad native to the Sonoran Desert in Arizona.
5-MeO-DMT is four to six times more powerful than its better-known cousin DMT, according to addictioncenter.com.
The drug's hallucinogenic effects can cause a "powerful religious-like" trip, and it appears to have motivated Tyson to get back into shape.
However, medical professionals warn that the drug is risky and potentially dangerous to humans, while the illegal collection of Collorado River toads for the drug trade is a threat to the species.
Tyson has long been open about experimenting with drugs and has a lucrative cannabis business called Tyson Holistic, where it is believed he earns around £500,000-per-month (NZ$1 million).
He is set to make even more in his boxing comeback fight, with Yahoo Sports' Kevin Iole reporting that Tyson will make a whopping $14.2 million from the bout, while his opponent Jones Jr. will be going home with $4.2 million.
Jones, 51, said during his weigh in that he expects his opponent to be competitive despite his age.
"He's been out 15 years and he knows what it's like to miss boxing," said Jones, "He realises what he had and he's seeking to get that back now … Now he has a desire to want to come out and be who he once was and do what he could once do."
Coverage of Tyson vs Jones Jr. starts at 3pm today and is available on pay-per-view on Sky Arena and Sky Sport Now.
Tune into NZ Herald for live updates of the fight later today.
READ MORE: All you need to know about Tyson v Jones Jr - Weird rules, start time, how to watch