Deimos was a demon, son of Aphrodite (Venus) and Ares (Mars). He had a twin brother, Phobos. Deimos was the god of fear and terror. He is depicted carrying a sword, known as Deimos' sword of dread. His Latin name is Formido, or Metus.
One of the moons of the planet Mars is named after Deimos. It is a dark, rocky moon about 12x16 km in size. It rotates around Mars about every 30 hours. It rises in the east and stays above the horizon for several days.