Mike with the Mask of Shadows on the N64 box art
The Mask of Shadows is a mask made out of bone that is implanted by Mama Nettie in Michael LeRoi's chest, held together by his ribs
mask being put on Mike '97 comic
and voodoo magic.
All of the other Shadow Men including Jack Boniface wore the mask on their face. Michael LeRoi has the mask sewn into his chest because Nettie's voodoo powers were weak and she had to 'cut corners' because of that weakness. Mike is a slave to the mask but he can use it to channel his powers of the ShadowGun to defeat the duppies of Deadside and prevent them from coming to the land of the living.
Jack Boniface ('92) with mask on his face