Desperation to survive can produce fear that is almost more dangerous than the actual threat itself. The threat in ‘Midnight’ is highly unconventional. Unlike almost every Doctor Who episode, you don’t actually see the monster which furthers the psychological horror of the story. The lack of a visual threat plays on humanity’s innate fear of the unknown, much like the iconic Weeping Angels whose true form is unknown. The inability to identify the Midnight’s entity increases its terrifying nature because there’s no way to fight it. You don’t know what you’re up against. On top of this, what little we do know about the entity is chilling in its own regard.
A focal point of the episode is the possession of Sky Silvestry. When the entity attacks the shuttle, Sky is convinced that it is after her. And indeed, when the dust has settled, the unseen monster has somehow taken control of her, using her as a vessel. Possessions have been a fixture of horror stories for centuries. From holy texts to The Exorcist, the concept of possessions plays on the natural, instinctive fear of not being in control of your own body. By possessing Sky and stealing her voice, the entity strips her identity, hollowing her out. It then uses Sky to rapidly develop knowledge of human speech and language. This in turn gives way to possessed Sky being able to convince the group to kill the Doctor. It creates the terrifying possibility of the entity using Sky or any other vessel to integrate itself into the human race and do anything it desires because it can keep changing hosts.
The entity seems to capitalize on emotions to gain access to people. First, it possesses Sky, who is recovering from a breakup, making her obviously more emotionally vulnerable than the other passengers. The entity also gains some level of control over the Tenth Doctor himself. The Tenth Doctor is arguably one of the most human incarnations of the Time Lords and as a result, it makes him more emotional which makes it easier for the entity to gain access to him. Additionally, the entity capitalizes on the group’s mistrust of the Doctor to divert their attention, knowing that killing him will set it free of any obstacles in his path to eventually take over the human race.