31 Monsters of October, Day 2: The Fiends

Real World Origin:
Film, Fiend Without a Face (1958)

In-Universe Description:
When an American airbase is established in rural Canada to test the feasibility and effectiveness of an atomic powered radar system, a scientist with unorthodox theories decides to take advantage of the energy radiated by the base's reactor. This leads to the creation of invisible horrors that latch onto their victims and suck out their brain and spinal cord. Later, when the creatures sabotage the base's nuclear reactor, making it run out of control, the true form of the fiends is made visible. The heroes of the film eventually find themselves trapped in a house and under siege by dozens of vampiric brains! Movie monsters rarely get better than this.