Amy Berg’s “Prophet’s Prey” is a chilling examination of religious madman Warren Jeffs, who is so drunk on his own power that he commits unspeakable acts upon the children of his followers.

Jeffs, the head of the Fundamentalist Church of Jesus Christ of Latter-Day Saints (FLDS Church), continues to exert a formidable hold on his thousands of followers even as he serves a life sentence for sexually assaulting minors. In fact, the criminal prosecution may have strengthened the bond between the self-appointed diviner and his faithful.

“He is more powerful from prison,” said Berg. “It’s proof the government is after all of them and persecuting them because of their religious preference. It becomes another wedge between their reality and the outside world’s.”

“Prophet’s Prey” is backed by Imagine Entertainment and Showtime and premieres at this year’s Sundance Film Festival. It draws heavily on the work of author Jon Krakauer, who examined Mormon fundamentalism in “Under the Banner of Heaven: A Story of Violent Faith.” The FLDS Church is a splinter group of the Church of Jesus Christ of Latter-day Saints, and is committed to the practice of polygamy.

It was Krakauer who helped tap Berg, the Oscar-nominated documentarian behind “Deliver Us From Evil,” a searing look at the Catholic Church’s sexual abuse scandal, to delve into another story of innocence abused.

Jeffs married underage women and assaulted boys and girls in his flock, but his predilections may have emerged from a different place than the priests who rocked the Catholic Church at its foundation.

“There are differentiations,” said Berg. “It was all about power with him. There was no preference between boys or girls or in terms of age…It’s not pedophilia or being a sexual predator in the typical sense. It’s really a deranged man using this and other things to explore his sick fantasies.”

In some respects, Jeffs is an unlikely messianic figure. “Prophet’s Prey” contains recordings of his sermons and reflections, and he is a drab, almost colorless figure, with little vocal fire or personal magnetism.

“He’s not charismatic,” said Berg. “Once you start meeting people he has influenced it makes more sense. He’s very monotone, almost hypnotic.”

Though Jeffs is imprisoned, there are many children still living in dangerous conditions, and Berg has her doubts that many members of the cult will be able to shake off their leader’s influence. From his cell, he continues to correspond with his followers, issuing apocalyptic warnings of imminent natural disasters.

“The only way people wake up is when they get excommunicated and can start rebuilding their lives,” said Berg.

There was also an impressive amount of hypocrisy when it came to how the prophet conducted his personal life. Jeffs preached about the evils of materialism, but amassed a fortune of more than $100 million by urging FLDS members to max out their credit cards and liquidate their worldly assets, handing over the cash to him and his church. He also traveled to places like Disney World, rode motorcycles and spent money in a way that he would have condemned from the pulpit.

So was he a true believer or a charlatan?

“He is a psychopathic narcissist and all the classic terms for a mad man,” said Berg. “I don’t think he consistently believes in himself, but he can convince himself that what he’s saying is true.”