Demi Moore reveals nude prosthetics from “The Substance”: 'Been holding on to these gems'

Moore campily showed off the extreme prosthetics used to depict her "Substance" character's tragic descent.

The Substance, one of the big art house hits of the fall movie season, is finally available to stream on MUBI. Star Demi Moore is celebrating in an unusual way.

"Spoiler alert," Moore wrote in a Thursday Instagram post. "Been holding onto these gems from [The Substance] and today feels like an appropriate day to share them. Happy Halloween from Elisabeth Sparkle."

The four-photo gallery features Moore in eerily lifelike prosthetics that transform her into a grizzled, warped, and distended old creature. In one she wears a prosthetic skin covering her top half and bike shorts while holding her micro-Chihuahua, Pilaf. In another, she takes a grimacing selfie splattered in fake blood.

The Substance follows Moore's Elisabeth Sparkle, a once renowned actress who's had to resort to Jane Fonda-style workout videos to get by. She begins taking a painful daily injectable that, to preserve the shock effect for those who haven't yet caught up with the film, bestows a newfoud youth upon her. But it comes with terrifying side effects.

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The latter half of the film explodes with blood (36,000 gallons, to be exact), guts, and tons of gnarly prosthetics. While there are brief respites of humor, they're a far cry from the hilarious behind-the-scenes shots Moore posted to her Instagram.

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Related: The Substance stars, director explain the film’s beautifully gruesome ending

When director Coralie Fargeat's body horror epic premiered in the official Competition at the Cannes Film Festival back in May, it garnered a 13-minute standing ovation from the crowd, one of the longest at that year's fest. Moore and her costar Margaret Qualley have been lauded for their fearless commitment to the violence and brutality required by their parts, but also for their raw, emotional vulnerability.

Moore told Entertainment Weekly that, in giving her the opportunity to access her full range, The Substance restored her excitement in acting, because prior to the film, she "went through a period of even questioning whether this is what I should still be doing. In the last four years or so, I felt that it was a personal question that I wanted to explore and see. Was this where I should be putting my energy?"

It was a period defined by "questioning my own ability, my own value, my own place" in the industry. In The Substance, Moore gets to train all that doubt, anxiety, and fear back on the industry and fire away with brutal force.

Related: Demi Moore, Margaret Qualley recall 'brutal,' bloody shoot for grotesque horror film The Substance: 'Can't f---ing move'

Qualley also recounted to EW how she "started sobbing" while rehearsing intense choreography.

"There's a feeling when you’re in a dance class with a room full of dancers and everyone is watching you trying to learn the choreography," she said. "Everyone already knew it, I was the only one that didn’t know it, Coralie was watching, it was one of my first days there... I was just like, 'I’ll be right back, I got this!' I just went to the bathroom and started sobbing and [then] was like, 'Do you think we could do this one-on-one for a while?' It was really outside my comfort zone. I’m not a natural."

The Substance is currently available to stream on MUBI.