Phobos is the personification of fear in Greek mythology. He is the offspring of Aphrodite and Ares. He was known for accompanying Ares into battle along with the ancient war goddess Enyo, the goddess of discord Eris (both sisters of Ares), and Phobos' twin brother Deimos (terror).
In Classical Greek mythology, Phobos is more of a personification of the fear brought by war and does not appear as a character in any myths. Timor or Timorus is his Roman equivalent. In Roman mythology, he has also been referred to as Pavor. Phobos is also said to be associated with Greek deity Pan.
Those who worshipped Phobos often made bloody sacrifices in his name. In Seven Against Thebes by Aeschylus, the seven warriors slaughter a bull over a black shield and then "touching the bull’s gore with their hands they swore an oath by chanting, "Phobos who delights in blood…". Ares’s son, Kyknos, "beheaded strangers who came along in order to build a temple to Phobos (fear) from the skulls."
Warriors and heroes who worshipped Phobos, such as Heracles and Agamemnon, carried shields with depictions of Phobos on them.
Because of Aphrodite being their mother, Phobos and Deimos were gods of the fear of loss.