Susano'o is a Japanese mythological deity who is best known as a mischievous storm god. After he was exiled from the heaven, he descended to the middle land and killed the gigantic serpent beast, Yamata-no-Orochi. He ruled as the lord of Izumo until he begrudgingly passed the right to his son-in-law, Oukuninushi.
He is the giant leader among the immortal forces. His mission is to hunt Da Ji and to stop Hydra's insurgence into the dimensional world. Although his goals match with the coalition's, Susano'o refuses to associate himself with humanity throughout the majority of the game. The immortal finds them to be unreliable and out of their depth, often defying their claims and promises due to his distrust in them. Therefore Susano'o, his loyal subordinate, and his army of mystics often act as a hostile third party within battle.
In the original timeline, it is said that he sought to fight the Hydra on his own, only to perish. While he apologizes to Kaguya for being so reckless, she assures him that his sacrifice enabled humanity to survive the Hydra's initial appearance long enough for her to come down from the Mystic Realm to save them. He also confirms to Kiyomori and Nezha that he was the one who resurrected them. In Kiyomori's case, it was to use him as an outlet for the Hydra's destructive power. In Nezha's, it was to allow him a second chance at life to fight.
When Kaguya takes the Coalition to Da Ji's past, before the Hydra, Susano'o is first encountered, allying himself with the Wei army at Tong Gate to chase Da Ji. Although the battle is lost, Susano'o is disgusted at how some humans and mystics chose to aid Da Ji. He later leads a mystic army at Yamazaki in the hopes of capturing Da Ji once again but is defeated. Nonetheless, he still chases her, and it is revealed that he has also been chasing Da Ji for Orochi's corpse, which was thought that she was attempting to revive Orochi. Susano'o later explains that the current world was supposed to destroy itself, but because Orochi was present, the world's "reason" fell to him. When Orochi was killed, the "reason" disappeared, and what remained was the manifestation of power which would become the Hydra. Unconvinced by the humans, he moved to prepare for a battle against the Hydra, and ended up attacking the Wu forces at Hefei led by Lu Xun but was repelled by coalition reinforcements led by Cao Pi.
After the coalition has defeated the eight Orochi figures scattered throughout the dimensional realm, they finally face Hydra's final form. Before they attack the beast at Koshi Castle, Susano'o blocks their path and demands that humanity prove their worth to him. Impressed upon his final defeat, he entrusts them with deciding the future of the realm. In the Good Ending's final battle, he will join the battle with the rest of the warlords and will immediately head out for Kiyomori before charging at Orochi X.
In the True Ending, he will only enter the battle after Orochi X is defeated. When the dimensional world crumbles apart, he willingly combines his power with the other mystics to ensure that humanity rightfully returns to their respective homes and time.
Warriors Orochi 3 Ultimate continues where the good ending left off with Susano'o fully aiding the human race for the first time. He is repeatedly mentioned by Fu Xi when Kaguya returns the mystic to his past, and Susano'o was stated to have been too busy exterminating demons when Orochi first emerged, but he sent Nezha and Sun Wukong to the Wuhang Mountains to unite the mystics against the serpent king. He is given two new scenarios. The first has him hypothetically receive Shennong's treatment after being wounded by the Hydra. With his wounds healed, he joins the chase for Da Ji at Sekigahara, but the continuous meddling of the humans allows her to escape. Shennong, who believed that the humans should have a just cause, voluntarily left Mystic Army after Susano'o's refusal to hear out the mortals. Later, he allows Sun Wukong to join Nezha in the chase for Da Ji, but she still escapes thanks to the humans and Kaguya. Although their struggles pique his interest, he deems them unworthy of saving the realm.
In Warriors Orochi 4, Susano'o and the Mystics were taken back in the dimensional world when it was recreated by Zeus, a god of Olympus, which again takes the humans he helped previously back to the realm. Susano'o arrived in the world having seen Nezha and Nuwa outnumbered fighting Ares and Athena, who were assisted by Cao Pi and Zhao Yun who have been empowered by the Ouroboros bracelets. Susano'o, Nuwa and Nezha held off the Olympian armies long enough for the humans to retreat. Meeting the humans once again and remembering their fight against the Hydra, Susano'o now willingly aids the humans in their fight; however, not wanting to risk direct confrontation with Olympus, Susano'o and the Mystics assisted the humans through information gathering. He along with Fu Xi at the episode of Orochi, the Serpent King, work together to fight along with humans once again, hoping for the real Orochi to come. And finally, he and Fu Xi managed to kill Orochi one more time.
And he is voiced by Troy Baker in the English dub and he is reprised by Kenji Hamada in the Japanese dub.