If you are hired to design an insane asylum, make it look like a big hood ornament, and put it right on the edge of a cliff overlooking the ocean. Light it poorly. Fix it so that when people want to get from the basement to the attic they only have to use one staircase, with about 10 shallow stairs. If you're ever stuck in a haunted insane asylum that looks like a big hood ornament on a cliff, and the lights are faltering, find a random wiring junction out of thousands in the walls of the basement, stick your hand in it and wiggle it around briefly. The lights will keep faltering just like they were, but everyone around you will somehow think you've rewired the building.
Evil looks a lot like black calamari.
You can keep it captive by walling it up in a basement room, but it can still mess with people's computers. If you want to drive someone crazy, show them a movie of a guy in a bowler hat bouncing a red ball. Also, include some underwater people, and make blood come out of their mouths. Do this over and over and over and over again, until you've completely numbed the audience to the effect. The characters were subtly developed and interesting.