Demons (1985)

Art imitating art is the basis of this demonic tale of a group of invited guests to the screening of a horror film that brings naturalism to life. They are baited and penned, and their walled-in feeling quickly turns to screaming fear as those who are dead lust after the flesh of the living. In this full-scale cinema of hell, it's only a question of time before demons from the abyss are asking for second portions.