We are the Onmyoji Brotherhood, and fate has ordained that we serve Lord Noah. In his name we shall strike you down.Yamatsumi, before battling the resistance
The Urabe clan was once a well-respected house of Doma, and fervent practitioners of Onmyodo. Charged with the oversight of the nation's religious affairs, they served at the pleasure of Doma's royal family for generations. Under the Empire's rule, however, any and all religious exercises were strictly forbidden, the Garleans believing they would invariably lead to the summoning of eikons. All known to be onmyoji, practitioners of this spiritual art, were kept under close watch. The viceroy Yotsuyu's treatment of these people was said to be especially cruel, bordering on the inhumane─a true test of faith, some would attest.
When the opportunity arose, a great many of the onmyoji fled from Doma, some choosing to go underground and form a resistance group. The Urabe family could not abandon their pride, nor could they shake their sense of duty to the royal family. And so they chose to stand and fight─a valiant-but-fruitless endeavor that would prove the end of that once-noble house.
At least, that is what the Empire was led to believe. In truth, a small number of the Urabe clan─led by Yamatsumi─would escape, assisted by none other than Noah van Gabranth. Thus would the Onmyoji Brotherhood rise from the ashes of the Urabe clan.
Where the Empire abhorred the onmyoji─often based on misguided principles─Gabranth saw untapped potential, which is why he offered Yamatsumi a place at his side. The Doman fugitive was understandably apprehensive until he came to learn of Gabranth's goals to not only reclaim Doma from the Empire, but ultimately build a prosperous new nation in Dalmasca. Gabranth was not at all the cruel, callous imperial Yamatsumi presumed him to be, and his earnestness proved enough for the onmyoji to pledge his services to the IVth Legion.
Having been handpicked by Gabranth himself, one might expect Yamatsumi to hold high station within the IVth Legion, but his position among the rank-and-file soldiers would lend him the freedom needed to better fulfill Gabranth's plans. Menenius took advantage of this state of affairs, tasking Yamatsumi and his cadre of mages with seeking out certain holy relics.
The onmyoji possessed a penchant for finding such artifacts, it would seem, for after he fled Doma, a holy artifact─the kami-no-iwato─was discovered in his possession. It is uncertain how this votive jewel found its way into his hands, but Yamatsumi claims it was originally bequeathed to the royal line of Doma by his forebears, and he merely claimed what was rightfully his. Doman officials, meanwhile, refute such claims, and have charged him with the crimes of larceny and treason.
Yamatsumi appears in the southern plateau in Zadnor with a cohort of mystics. He is confronted by a resistance fighter who asks them to identify themselves. Yamatsumi reveals that he is part of the Onmyoji Brotherhood who serves Noah van Gabranth before engaging the resistance in battle. Marsak sees that his allies need help and he joins the fray, only for yamatsumi to even the odds by summoning a shikigami to assist him in battle. In the end his men and monster are defeated, and he retreats to the western plateau.
Yamatsumi is tracked down by Oboro Torioi and Tsubame Oshidari along with Nagxian soldiers to confront him for his criminal acts. He states that under Yotsuyu's rule, they suffered and endured her wrath, only to be saved by Noah, and he plans on repaying his kindness with delivering him that treasure. During battle he summons a shikigami Tenma to assist him, only for him and it to be defeated. Oboro offers him a chance to return to Doma, only for Yamatsumi to refute by claiming he swore his life to Noah, before popping a smoke screen and vanishing.
Upon the Northern Plateau, Yamatsumi summons his strongest shikigami, the monster Yoki. His summon is defeated however, and he is hard pressed against the resistance and attempts to escape before being cornered by Atori and Kosyu. Unable to flee, he is confronted by Gilbrisbert who tells him to speak his most earnest wish to the auracite he has with him. As he reveals he wants to see the Onmyoji revived under a new nation, he hears a voice from within the stone before turning into the Lucavi Famfrit. He fights the resistance in this form with Gilbrisbert but the two are defeated, and Yamatsumi perishes.
Yamatsumi is a far eastern hyur with long black hair and discolored eyes, one being red and the other being a white color. He wars a beak face mask called a Karasu Bo and wear's an Ivalician Oracle's coat. In battle he wields the Ruby Tide Grimoire.
Yamatsumi is devoted to Noah van Gabranth who he sees as his savior from Yotsuyu's rule in Doma. He is steadfastly loyal and fights to see the Onmyoji be reborn.
Yamatsumi appears as an enemy in Zadnor, he appears in the skirmishes Deadly Divination, A Just Pursuit, Mean-spirited, and again in A Relic Unleashed. He uses his own Ruin spell called Illumination, and a gravity spell called Inhibition. During his fights he summons Shikigami to assist him as well as protect him from harm.
- Final Fantasy XIV, Field Notes on Yamatsumi