In the God of war series

Early life

Deimos was born a few years after Kratos, and bore a remarkable birthmark across his body. The two brothers grew up together under the watchful eye of their mother Callisto inSparta, with dreams of joining the Spartan Army when they were older. Kratos and Deimos trained with the traditional spear and shield throughout their childhood, with Kratos teaching the young Deimos to remember that "a Spartan never lets his back hit the ground."

The Marked One Prophecy

Long ago, an Oracle foretold the destruction of the Olympians at the hands of a Marked Warrior. Due to his unusual birthmark, the Gods feared that Deimos would be the prophesied warrior, so they devised a plan to abduct him from his family so that the Oracle's prophecy wouldn't come to pass.

One fateful day, Ares and Athena descended onto Sparta to take Deimos, unleashing an army of Centaurs to decimate the populace while they searched for him. They quickly found the young Deimos amidst the chaos and took him while he was training with Kratos, though his brother attempted to stop Ares. Kratos lunged at Ares to keep him from taking his brother but Ares struck him down, scarring him over his right eye. Ares then attempted to kill Kratos, but Athena quickly told him not to, as they already had what they where looking for. Ares then disappeared in a cloud of fire. Athena apologized to Kratos, then disappeared in a cloud of fire.

Ares brought Deimos to Thanatos in the Domain of Death to remain there in torment, ensuring the prophecy of "the Marked One" would never occur. For several years, Deimos believed Kratos would come to his rescue. As time passed, his hope began to fade, and was replaced with hatred for the brother who left him to rot.

Greek Mythology

In Greek mythology, Deimos (Ancient Greek: Δεῖμος, pronounced [dêːmos], meaning "dread") was the personification of terror.

He was the son of Ares and Aphrodite. He is the twin brother of Phobos and the goddess Enyo who accompanied Ares into battle, as well as his father's attendants, Trembling, Fear, Dread and Panic. Deimos is more of a personification and an abstraction of the sheer terror that is brought by war and he never appeared as an actual character in any story in Greek Mythology. His Roman equivalent was Formido or Metus

God of War: Ghost of Sparta

“	Did you think I would forget? Did you think that I would forgive? I will never forgive you, brother!	”
–Deimos upon being found by Kratos.

After having met -and defeated- Callisto in Atlantis, Kratos was compelled to find his brother at any cost. Undertaking a perilous journey that took him across Greece, Kratos finally found Deimos deep in the Temple of Thanatos, suspended from a tree.

Freed from his chains, save for a single massive gauntlet locked around his right arm, Deimos wanted revenge against Kratos for not protecting him and quickly assaulted his brother.

After a grueling battle, Deimos tackled Kratos over a ledge and proceeded to pummel his brother into submission, using the gauntlet. As Kratos lay bloodied and beaten, Deimos saw his final blow shatter the gauntlet.

Willing to continue barehanded, Deimos was instead interrupted, as Thanatos arrived grabbed Deimos, taking him to the Suicide Bluffs to throw him off the edge. Kratos, barely able to stand, managed to follow them to the Bluffs.

Locked in combat, Deimos and Thanatos never saw Kratos arrive, until the Spartan raced for the edge, after Thanatos managed to throw Deimos off. Rushing over to his brother, barely saving him from certain death, Kratos proclaimed never to leave Deimos again, and gave Deimos the Arms of Sparta.

Joining forces, side by side, as brothers, Deimos and Kratos began their attack on Thanatos. Together, the pair followed Thanatos along the cliffs and eventually caught up with him, where Thanatos stated Ares had chosen poorly, where he should have opted for Kratos instead of Deimos, all those years ago.

The Spartan brothers charged Thanatos, fighting the God of Death together, until Thanatos transformed into a gigantic winged monster and grabbed Deimos, crushing him against the cliff side, effectively killing him. Kratos, fueled by extreme rage, unleashed Thera's Bane at an unhuman level, and defeated Thanatos.

Kratos carried Deimos' lifeless body to the top of the Suicide Bluffs via the Path of Solitude, where the Grave Diggerhad prepared a grave for Deimos. He then lay Deimos' body into the grave, stating Deimos was now free, Kratos also make a promise to Athena that the gods would pay for what they did to his brother.

Deimos Weapons and Powers

Deimos was an incredibly powerful mortal as he was able to best Kratos, a god, in single combat armed with only a gauntlet. For this reason it is presumed that it's because of his demigod attributes due to being a son of Zeus just like his brother.

Deimos is also extremely proficient with the Arms of Sparta as he wielded them to great effect in the fight against Thanatos. He is also capable of having incredible strength from being able to overpower Kratos.

It might also be possible that Deimos was able to overpower him because Kratos had let him win as seen in the remastered PS3 version the player get an achievement called "Let Him Win"