Kratos is the main protagonist of the God of War video game series.

Kratos became the captain of a rapidly growing Spartan army, first with only fifty men that grew into the thousands. He won many victories and brought many treasures back to his family. He gave his wife a jeweled necklace, and his daughter Calliope a carved wooden flute.

But soon, Kratos became brutal, winning battles through brutal, unorthodox but effective tactics. Only his family was brave enough to question his motives. He claims he wants the world to know of the glory of Sparta, but his wife protested he was just doing it for himself.

However, one day he and his Spartan army were no match for the merciless barbarian tribes of the east. Being outnumbered and overpowered, his army was losing the battle. Kratos, about to be killed by the barbarians' leader, pledged himself to Ares, the God of War, in exchange for victory. The god accepted and wiped out the barbarians, giving Kratos the Blades of Chaos as a sign of his servitude.

Kratos served Ares loyally, but Ares later tricked him into killing his wife and child in order to make him into a perfect warrior. Stricken with horror and grief, Kratos left the bodies to be burned with the temple as he cursed Ares's name. The village oracle declared he is to be cursed to wear their ashes for all time on his skin to serve as punishment for his actions. From that day forward became known as "The Ghost of Sparta" because of his skin now "pale as the moon" from the ashes that coated him. Aterward, the distraught Kratos began to be haunted by terrible nightmares of the deaths of his family. Over time, the memories and nightmares of killing his family began to drive him into total insanity. Abandoning Sparta, Kratos traveled throughout Greece, only finding some solace in sailing the Aegean Sea. To find peace, he pledged his life and services to the other gods of Olympus in the hope that they would one day relieve him of his burden.

To other mortals, he was now marked by his white skin. The knowledge of his past actions have been shown to repulse normal people to the point where they do not allow him to save their lives, even killing themselves in the process. He was forever known as the "Ghost of Sparta" to all who saw him; the epitomy of cruelty and selfishness.

Kratos would serve the gods for ten years following the death of his family, but always held on to the desire for revenge against Ares.

For 10 years Kratos served the Gods to rid him of the pain and madness caused by the nightmares of the murder of his family. But no matter how many battles he fought or women he took to his bed, there was no escape from his punishment. Halfway through his servitude, he was sent to defend Attica against the Persians, while at the same time, fought a basilisk. While chasing the former, he kills the Persian King and then kills the former. He is soon witness to the sun falling from the sky, plunging the world into darkness. He follows it through Marathon and the black fog of Morpheus. When he arrives at the Temple of Helios, a statue of Athena tells him that Helios has disappeared and Morpheus caused the gods to fall "into a deep slumber". He is then tasked to rescue Helios and to stop Morpheus.

Along the way, he hears a familiar melody, which he recognizes as a song played by his daughter Calliope. He meets Eos, who says the gods will relieve him of his nightmares if he saves Helios from Atlas. Bringing Fire Steeds to life, Kratos goes into the Underworld but is denied passage from Charon, who casts him into Tartarus. Kratos is able to escape and defeat the ferryman, using the Gauntlet of Zeus from his temple. After taking his boat, Kratos sees Calliope and goes after her. But when he arrives at the Temple of Persephone, he doesn't find his daughter but the goddess herself, the Queen of the Underworld. Persephone tells him his daughter is in Elysium Fields and the only way to see her is to relinquish his past deeds and powers given to him by the gods. But when he gives his power to the Forsaken Tree, Persephone reveals that she released Atlas to destroy the pillar that holds the world, in revenge for the betrayal of her family that ended up in her marriage to Hades.

Realizing he was causing his daughter's death again, Kratos abandons hope of seeing her again to stop Persephone. He recovers his powers and weapons and follows her to the pillar, where he chains Atlas to the pillar and defeats Persephone. Before her last breath, she warns that his suffering will never end. He resolves to continue serving the gods so they will keep their promise to rid him of this nightmares; Atlas asks about the promise of an Olympian, and swears that they will meet again. Kratos then returns Helios to the sky, but is weakened from the battle and falls down to Earth. Athena and Helios appear, and take the Gauntlet of Zeus and the Sun Shield away from him.

Ten years later, after killing the sea monster known as The Hydra, Kratos got a chance to seek his revenge on the God of War and rid himself of the terrible nightmares that haunted him. He is ordered by Athena to seek out Pandora's Box in order to help him destroy Ares.

Following an Athenian Oracle's instructions, Kratos traversed the Desert of Lost Souls and found Pandora's Temple atop the back of the Titan Cronos. He made his way through the temple and retrieved Pandora's Box. After obtaining Pandora's Box, Ares hurls a huge broken Greek pillar towards The Temple of Pandora. The pillar impales and kills Kratos, sending him to Hades as Harpies take the Box. During the fall to the River Styx, Kratos is able to grab onto a ledge and then escapes the clutches of Hades. He is helped by the Gravedigger he met earlier. He then reacquires Pandora's Box from Ares and uses it to grow as large as the god. After a hard fight, Ares sucks Kratos into a void where four monstrous incarnations of himself were attempting to kill his family. He tries to save them but Ares strips him of the Blades of Chaos to murder his family again. When he snaps back into the real world, Ares is prepared to deliver the final blow, Kratos notices the Blade of the Gods, which connects Athens to a temple and uses it to destroy the God of War.

Though his past had been forgiven, the gods could not relieve Kratos of his nightmares. His last hope taken from him, Kratos attempted to commit suicide by jumping off a cliff. Athena had a different plan for the Spartan. She saved his life and offered him the empty throne on Olympus. He entered the portal to Olympus and settled himself on Ares' throne, surrounded by statues of the great enemies he had bested. For all time, whenever and wherever battles were to be fought, for good or evil, they would be under the watchful eye of Kratos, the God of War.

As the new God of War, Kratos continued his conquests, favouring his homeland of Sparta over all other nations. He ordered his Spartan legions to attack other cities, such as Rhodes, only taking solace in war and bloodshed, anything that would distract him from his nightmares. He does not listen to Athena's warnings not to upset the Gods and plunges down to Earth, wrecking havoc on the city. But then an eagle (who he thinks is Athena), robs him of most of his godly power - causing him to shrink to the size of a mortal man - and places it in the Colossus of Rhodes, bringing it to life. Kratos fights a long and hard battle with the giant until Zeus offers help in the form of the Blade of Olympus, which was used to end the Titan War. Infusing all of his powers and immortality into the blade, Kratos takes down his foe. As he shouts to the heavens, asking if he needed anything more to prove, the Colossus' falling hand crushes him. He began limping his way to the blade to save himself, only for the eagle to reveal itself to be Zeus, who explains he's trying to save Olympus from the same fate as Ares. The King of the Gods takes the blade and drives it into his chest, telling him he will never will rule Olympus and all will suffer for his sacrilege. With a swing, he destroys all warriors in the city. With his last breath Kratos swears Zeus will pay.

Kratos is then dragged down by the arms of the Underworld, but the Titan Gaia, who has been watching him his whole life, saves him, sealing his wound and giving him back the strength to escape death once again. He climbs out from the Underworld back into Rhodes, where he instructs a surviving soldier to return to Sparta for another battle. He takes Pegasus to fly back to Olympus so he could exact his revenge but the flaming winged horse would not listen to him. Gaia told him to seek out the Sisters of Fate so that he may travel back in time to reclaim the Blade of Olympus to take his revenge on Zeus. Kratos goes to Typhon's lair, where he meets Prometheus, who pleads him to release him from his torment in the fire of Olympus. Kratos takes a bow from Typhon and uses it against Prometheus' last chain, burning his flesh and his ashes granted him a Titan power. Kratos safely arrived on the Island of Creation, where he meets Theseus, who guards the Sisters. They fight to determine who is the best warrior; Perseus to save his beloved Andromeda; the Barbarian King who escaped Hades' torment to change his fate; and Icarus, who has gone crazy. After defeating them all, gaining valuable items form them, he falls into the Underworld once again, where he meets Atlas. The Titan is intent on crushing the former god for his imprisonment but Kratos promises to change his fate in exchange for his help. When he gets back to the surface, he accidentally wounds the Spartan soldier from earlier, who tells him that Zeus destroyed Sparta for serving Kratos. As he shouts out his anger, he is attacked by the Kraken. As he is held in the beast's grasp, Kratos sees his wife, which is actually Gaia, who encourages him to go on or face eternal torment in Hades.

Kratos soon meets with Lahkesis, who tells him that the Fates decide the destinies of all and that she allowed him to come this far. However, she proclaims that it is not his destiny to kill Zeus. Kratos declares that she no longer controls his destiny before battling her, but she then summons Atropos, who takes him back in time to his battle with Ares, determined to destroy the Blade of the Gods, so he'd die in the present. He stops her and flings them back to the present. He fights both of the Fates and traps them in a mirror and then shatters it. He then goes to Clotho, who warns him not to go forward with his manipulation of fate. He kills her and takes control of the Loom Chamber, going back in time to take the Blade of Olympus back from Zeus, pulling it out of his other self. They fight on the Summit of Sacrifice. When Zeus unleashes a powerful lightning storm, Kratos yields defeat and surrenders. He asks to be put out of his misery. Zeus promises him a quick death, stating, "I will release you from your life my son, but your torment is just beginning." Kratos dodges the blow and pins Zeus to a rock with his blades. He then takes up the Blade of Olympus and drives it into Zeus' abdomen. He is stopped by Athena, who is willing to defend Olympus. As Zeus tries to flee, Kratos makes one more attempt on him, only for Athena to take the blow. Her dying words reveal that Zeus is his father and was hoping to break the cycle of son-killing-father. Zeus has to live so Olympus will prevail. Kratos snarls he has no father and declares that the time of the Gods is at an end. He goes back in the chamber of Loom, go back to the great war of the gods and the titans and bring the titans back from the past and they climb up to kill Zeus.

Returning to the Loom, Kratos traveled back in time to the Great Titan War and took the Titans back to the present. As the game closed, he led them in an assault on Mount Olympus, declaring "Zeus, your son has returned! I bring the destruction of Olympus!"