About Bane’s mask, Tom Hardy’s skull and Tom’s generally astounding ways, from the production notes for The Dark Knight Rises:
Obviously, Bane’s most distinctive feature is the menacing-looking mask, fastened to his face, which continually pumps pain medication into him, keeping the agony from his violent past at bay. “His life depends on it,” Nolan states. “This is somebody whose history is carried with him in a very visible way on his face, making him, in a very real sense, monstrous.”
“We designed the mask to be animalistic,” Hemming says. “It had to look completely different from Batman’s cowl…and it could not be black.” The mask was built by the costume effects department, using a digitally mapped model of Tom Hardy’s face and skull. Costume effects supervisor Graham Churchyard explains, “To us, the Bane mask had to fit like a prosthetic; however, unlike a prosthetic, it had to look like it was engineered out of metal. We were able to take Tom’s computer cast and 3D model each rigid piece to the contours of his head so it was tight to his face, with no gaps.”
As it turned out, “tight” was an understatement. Hemming attests, “It was gripping Tom’s head like a vice. With his assistance and patience, we made it as tight as it could ever have been. There was a magnetic removal panel on the front, so everything you see has a series of magnets underneath it, and everything beneath that 14 has a rubber seal that pressed into Tom’s skin and was held on by tension. The fact that he tolerated it, let alone acted with it, was astounding.”
(Source: thedarkknightrises.warnerbros.com)

