Nightmare Fuel / The Darkest Hour

• What the aliens actually look like is scary in and of itself: they look like some kind of robot octopus from Hell.
  • They're pretty terrifying before they're revealed, as well. They're almost completely invisible, the only sign of their approach being that electronics go haywire in their presence. And one touch from their shields turns you to charcoal dust. Seems nothing really is scarier.