Ghost Adventures

"Ghost Adventures" host Zak Bagans has taken on his most terrifying project yet -- he just bought a house in Indiana ... believed to be the site of one of the most terrifying demonic possessions ever ... a rumored "portal to hell."

The house rose to fame in 2012 ... after a mother who lived there reported her 12-year-old daughter and 9-year-old son had been possessed. Shockingly, there are even docs from child protective services that back up her claims.

Among the many scary incidents ... the mother says she witnessed her daughter levitating above her bed.

She also said she saw her son walking on their ceiling ... an account corroborated by several other witnesses. The mother did everything she could to de-demonize the house -- including building an altar and hiring an exorcist -- but nothing worked and she eventually moved.

Zak tells us, he caught wind of the horrifying tale and made an offer to purchase the home for $35,000 -- the owner was all too willing to sell.

The photo shown above is an actual police photo of the house ... and it's hard to miss what looks like an apparition in the window.

Zak says he's going to live there and document his experience -- "If it's true this home is a portal to hell, then I want to go there and see what happens."

Balls of steel.

Check out the CPS report (below) ... detailing the family's frightening claims.

Never bring your work home with you -- especially if your job involves ghost-hunting and human skulls -- because you could end up with one pissed-off spirit haunting your house ... and pushing your friends down stairs.

"Ghost Adventures" star Zak Bagans tells TMZ, the supernatural encounters began after he found a human skull during an investigation last month at an old mining town hotel -- and genius actually decided to bring the remains home with him.

Zak -- who built a display for the skull in the basement of his Las Vegas home -- tells us, he noticed a huge surge in paranormal activity almost instantly ... an angry, demonic-type presence that had never been in his house before.

On one night, Zak tells us, he was woken up by a slight pressure on his ankles -- what felt like hands grabbing him -- and all of a sudden, the force yanked him several inches down in his bed.

Days later, Zak says he had a girl over at his house -- and out of nowhere, she spilled head over heels down his stairs ... insisting someone ... or something ... had pushed her.

But that's just the tip of the iceberg -- and Zak tells us, he's so terrified ... he hired a local bishop to perform an exorcism at his house in the next two weeks

As we previously reported, the ghost seekers contacted people at "Idol" to investigate the mansion ... after the contestants living there claimed the place was haunted -- but we're told, the owner of the house quickly shut down the whole operation.

Zak Bagans -- lead paranormal investigator -- tells us, the owner was worried about all the ghost-infestation publicity ... and wanted to ward off any more possibly negative attention.