The Greek god who personifies fear and is the son of Ares is Phobos.
Phobos embodies fear and panic, particularly the terror produced by war. Hesiod’s Theogony names him as a son of Ares, the war god, and Aphrodite, the goddess of love. He is the brother of Deimos, whose name means dread or terror, and the two often accompany their father into battle.
In Homer’s Iliad, Phobos and Deimos appear among the forces surrounding Ares. They are not simply interchangeable names for fear: Phobos is the immediate feeling of fear or flight, while Deimos represents dread and terror. The distinction is reflected in their Greek names and in later interpretations of the pair.
Phobos has relatively few independent myths, but he appears in battle scenes and on heroic shields. In Aeschylus’s Seven Against Thebes, warriors invoke him alongside Ares and Enyo. According to Plutarch, Alexander the Great sacrificed to Phobos before the Battle of Gaugamela, hoping fear would affect the enemy. Mars’s moon Phobos was named after this personification.