|“||Besides, I love terror. I live on terror!||”|
Early lifePhobos was born to Ares and Aphrodite.
Along with his twin brother Deimos, Phobos would often accompanies Ares in battle.
Angry that their sister Clarisse La Rue was allowed to ride in Ares' chariot because they usually use the chariot, Phobos and Deimos decide to steal it from her. They then hide it in the Staten Island Zoo, and use it as bait to catch their sister and Percy Jackson.
Deimos fights Percy but is defeated and disappeared. Deimos changed his appearance to match Ares in order to scare Clarisse, but he disappeared again after she overcame her fear.
While underground in Phobos's and Deimos's temple, Piper McLean and Annabeth Chase fight the giant Mimas. Piper sacrifices her cornucopia to her brothers. After Mimas's defeat, the face of Deimos on the wall falls onto the giant, killing him. As only a god and demigod together can kill a giant, presumably Deimos caused this to happen to kill Mimas. Then Piper thanks her brothers, and requests a way out of the cave. Phobos opens up a tunnel for them to get back to the surface along his twin.
Deimos is known to be more aggressive than his brother, Phobos.
Despite his cold behavior towards Clarisse, Deimos isn't all that bad, as he accepted his other half-sister Piper's request for help.
Deimos is described as a muscular teenage boy with a brutal face covered with scars. He is dressed in jeans, a black shirt, and a leather jacket.
Deimos has the standard powers of a god.
- Odikinesis: As the god of personal fear, panic and rout, Deimos can control the feelings and emotions of war, such as fear, hate and rage.
- Persona Worst Fear Generation: Phobos has the ability to make individuals see their worst fears through eye contact. In The Demigod Files, Clarisse saw her father in a fury and Percy saw all his friends from Camp Half-Blood in flames. However, Phobos can only do this to one person at a time.
- Teleportation: Deimos can vanish to other locations.
- Cult Juridisdiction: Deimos has control over objects which represents him. In The Blood of Olympus, he was able to bring a statue of himself down upon Mimas without being physically present.
- Shapeshifting: As a god, Deimos can change his appearance and form. In The Demigod Files, he changed his appearance to look like his father.
- Swordsmanship: Deimos is a sword fighter. Despite of being a son of a war god, he is a terrible physical combatant likely because he never had to rely on his skill and thus never trained.
- His alternate name is Deimus.
- When questioned about the difference between the two it was stated Phobos typically acts on one person at a time and makes it more personal and specific while Deimos acts on a larger scale, such as whole crowds.
- Deimos, the smaller of the two moons of Mars, is named after this deity.