He's one of the biggest box-office draws in history, but in recent years Tom Cruise has become more than just the face of his films. He has also become the face of his religion -- Scientology.

A recent video of Cruise -- made for a Scientology event and leaked online -- showed the star's unbridled passion for his religion and piqued the public's interest in a belief system that has long been surrounded by controversy.

"I think it's a privilege to call yourself a Scientologist," Cruise said in the video.

Cruise is a vocal supporter and close friend of Scientology's worldwide leader, David Miscavige, who took over the reins of power when science fiction author and founder L. Ron Hubbard died in 1986.

Miscavige says Scientology can offer its followers greater ability in all areas of life, rid people of negativity, and make them "clear."

But some former members of the Sea Organization, or Sea Org (Scientology's version of clergy -- the group of people who essentially run the church), including a niece of Miscavige, see another side to the religion. They spoke to "Nightline" about how they became increasingly disillusioned with the Church of Scientology, until they decided it was time to leave.