Legendary Pictures / Universal Pictures 1 / 7
Legendary Pictures / Universal Pictures 1 / 7

Jessica Chastain is set to get up close and personal with the things that go bump in the night when "Crimson Peak" debuts on Oct. 16, 2015. But the real horror of the gothic romance, which co-stars Tom Hiddleston and Mia Wasikowska, were the costumes, says the redheaded beauty.

"In the biography [writer-director] Guillermo [del Toro] sent me, it said that my character liked very tight, restrictive clothing: tight corsets, velvet dresses that went up to my neck, long-sleeve gloves -- usually it was only my face that was getting air during the day," the Oscar nominee exclusively told Wonderwall.com while promoting "Crimson Peak" at Comic-Con 2015.

"A couple times I had to sit down and be like, 'I understand now why women fainted all the time in the past,'" she added.

In "Crimson Peak," Jessica portrays Lady Lucille Sharpe, the villainous sister of Tom Hiddleston's mysterious Sir Thomas Sharpe. ("She's never played a dark, heavy character, and I hope, I feel, I believe that she's done a villain for the ages on this one," writer-director Guillermo del Toro told us.)

Portraying the 6'2" actor's sibling proved to be yet another challenge to the petite actress: "I'm 5'4" in real life, so in the film I wore seven-inch platforms under my dress because I play Tom Hiddleston's sister, and he's, like, ginormous," she dished.

Her feet weren't the only part of her body that was burdened during filming: "I had a wig that went all the way down to my feet, so that was usually in a big bun behind my head," Jessica revealed.

So what exactly was the worst part of her wardrobe? "Running in all of that," she says. "There were a couple times I had to run, and I was like, 'This is tough.'"

But in spite of all that, the "Zero Dark Thirty" actress claims she "loved the transformative nature of the costumes" while shooting "Crimson Peak."

Talk about suffering in the name of art!