Avad is the 14th Sun-King of the Carja tribe in Horizon Zero Dawn. He killed his father, the 13th Sun-King Jiran, after becoming appalled by his father's brutal reign and his role in the Red Raids. Avad seeks to reform the Carja and rule his kingdom with a fair and kinder hand.
During the Red Raids, Avad was wary of his father's commitment to human sacrifices. He became interested in a prisoner taken during the Red Raids, a fierce Oseram woman named Ersa who had managed to prevent herself from being sacrificed after surviving in the Sun-Ring. For her actions, she was made a palace slave. Avad befriended Ersa and helped her to escape.
Avad's shaky relationship with his father erupted in bloodshed in 3038, when his eldest brother and the favored heir to Jiran's throne, Kadaman, was executed by his own father for demanding an end to the Red Raids. Finally realizing the King must be stopped, Avad and his loyal soldiers fled from Meridian and traveled to the Claim in search of strong Oseram allies. Avad reunited with Ersa and with her help managed to form a warband of Oseram Freebooters willing to fight to overthrow Jiran.
Avad planned to avoid a drawn-out war between the Carja and Oseram by using his status as the rightful heir to the throne of the Sun to inspire his people, usually wary of tribal outsiders, to rebel against the Mad King and rally behind the Oseram allies.
The Liberation of Meridian
After months of preparation, Avad and his allies marched on Meridian. In an effort to limit the damage to the city, Avad had some of his forces infiltrate Meridian while destroying the outer walls and city gates with cannon fire. Avad's plan worked, as Jiran's forces were thrown into chaos and Avad managed to capture the city. Avad then personally confronted his father and tried to convince him to surrender peacefully. Jiran refused and Avad reluctantly slew him. This made Avad the 14th Sun-King, and the first to ascend the throne through an act of patricide.
After becoming the 14th Sun-King, Avad began a program of extensive reforms throughout the Sundom. He abolished slavery, ended the human sacrifice to the Sun, mandated the elimination of all gender discrimination in Carja institutions (such as the armed forces and the Hunters Lodge), and welcomed all foreigners to Meridian. He also made the Oseram Freebooters from his rebellion into his personal Vanguard, with Ersa as their Captain.
Avad and Ersa also began an affair, which they both kept secret, since Avad feared that the Carja nobility (who were very reticent to accept his end to tribal discrimination) would rebel if it became public knowledge that the King was involved with an Oseram woman, nor would the Oseram accept the relationship.
Carja Civil War
The Liberation marked the beginning of the Carja civil war: Jiran's supporters retreated to Sunfall, deeming themselves the Shadow Carja. The Carja in Shadow refused to serve Avad, labelling him a tyrant for murdering Jiran and deeming Itamen, Avad's younger brother, as Jiran's true successor.
Two years into his reign, Avad sent a convoy to the Nora tribe as a gesture of peace. Soon after, Ersa was found dead at Red Ridge Pass, apparently murdered by the Shadow Carja. In response, Meridian was closed off to outsiders, and Ersa's brother Erend was appointed Captain of the Vanguard. Upon discovering that Ersa's death had been faked, Avad was introduced Aloy, a Seeker from the Nora who had come to Meridian investigating a recent attack on her own people. After coming to the conclusion that an Oseram named Dervahl was behind Ersa's kidnapping, Avad asked for Aloy's help to deal with the threat.
Battle for the Spire
Sometime later, Avad was approached again by Aloy, warning him of an upcoming attack by the Eclipse. Though reluctant to fight, Avad ordered the defense of Meridian, and successfully repelled the assault on the city with Aloy's help.
Avad is a reasonable and generally benevolent man, much unlike his father Jiran. He strives to unite all tribes in harmony, as well as reform the Carja into a more equal society. Despite his grand goals and achievements, Avad is a somewhat meek man, responding shyly to praise and seeking to find compromises that benefit as many people as possible in order to avoid making enemies. He also seems to be attracted to strong, dominant women, as evidenced by his passionate love for (and secret affair with) Ersa, as well as his attraction to Aloy.
Despite Avad's grand ambitions, he understands that "change won't come in a single sunrise", and that fulfilling his goals will take time.