The phrase "real demons" is used to describe people or things that are extremely challenging, harmful, or evil. It suggests that the troubles or problems they cause are difficult to overcome. Full definition
While testing, I swear that I felt that there might be real demons inside my games. (thebuttonsmashers.com)
During his unique entrance (an intentionally difficult yet memorable shot that echoes Bond's own introduction in the film), Bardem weaves a wild monologue about rats eating rats to be a haunting, finite revelation of an impassioned mad man whose very real demons contribute to Skyfall's wonderful tension. (thescorecardreview.com)
And once in a weakened state, leads into the third stage, possession...» (Referenced from: Ahh Real Demons!) (elearningindustry.com)