Angelina Jolie thought it was "romantic" to wear Billy Bob Thornton's blood around her neck.
The 'Maleficent' actress and her ex-husband - who she married in 2000 and split from two years later - famously wore the vials of fluid during their relationship and the 'Fargo' star insists it was his former spouse's idea to cut their fingers to get the blood and wear them to feel closer to one another when they were working apart.
Speaking to students at Loyola Marymount University's School of Film & Television, he said: "A vial of blood is very simple. Angie came home one day with a kit she bought.
"You know those lockets you buy that are clear and you put a picture of your granny in it or something like that and wear it around your neck? That's what it was. She bought two of those. We were apart a lot because she's off making 'Tomb Raider' and I'm making 'Monster's Ball.' We were on opposite ends - we see each other for two weeks and whatever.
"She thought it would be interesting and romantic if we took a little razorblade and sliced our fingers, smeared a little blood on these lockets and you wear it around your neck just like you wear your son or daughter's baby hair in one. Same thing."
The 59-year-old star joked the gesture was then exaggerated in reports.
He said: "From that, we were wearing quart jars of blood around our necks.
"And we were vampires and we lived in a dungeon."
The five-times married star insisted he prefers to be upfront about his past and thinks he is unusual in that respect.
He said: "I think it's your duty to kind of tell people the truth about this stuff and the truth is not encouraged anymore."