"For me, in my filmography of work, this is the most challenging role I have done and I don't think I can get better than this," said Bipasha.
"Everyday was a struggle, I was emotionally drained, exhausted. I wanted to finish it soon because it was really disturbing me," she added.
"Raaz 3", slated to release Sep 7, deals with the subject of black magic.
Bipasha says while everyone on the sets of the film was under a lot of pressure for different reasons, her co-star Emraan Hashmi was the only one most relaxed.
"Everyone was very lost on the sets. Vikram (Bhatt) was under a lot of pressure because he had to make a film better that 'Raaz'. I had taken the challenge of playing Shanaya, which is the darkest character that any Hindi actress has ever played on screen.
"So everyone was a little lost... Esha (Gupta) was just saying that she was troubled because she doesn't even know what she wants to do in life. But amongst all us troubled people there was Emraan Hashmi who was sitting relaxed and the moment they said the shot is ready, he'll get up," the 33-year-old said here.
Bipasha is in awe of Emraan's working style.
"You will think that he is not involved but then when he comes and you say 'Action', he just pounces on the roll! He is that kind of a fiery actor," she added.