Coralie Fargeat's bloody-as-hell satire lets the star flip the bird to showbiz's youth obsessions and beauty double standards - in the best (and grossest) way imaginable

From daunting high-energy choreography to nine-hour prosthetic application, the stars tell EW "The Substance" was a satisfyingly grueling, months-long shoot.

Demi Moore, Margaret Qualley, Dennis Quaid and more stars hit the red carpet for the L.A. premiere of their film, 'The Substance.' See all the photos.