Yhwach is a Quincy and the Emperor of the Vandenreich. A thousand years before the start of the events of BLEACH, he and Captain-Commander Genryusai Shigekuni Yamamoto came into conflict, and Yamamoto failed to kill Yhwach. Yhwach is a formidable warrior and can take down even incredibly powerful opponents using his immense strength and array of abilities. He has a callous disliking for his lower-ranked underlings, believing them to be little more than disposable fodder. Despite his reckless disregard for his petty subordinates, Yhwach claims to hate seeing those under him fight one another in public.
Some time after Sosuke Aizen attempted to become a god, Yhwach resurfaced with his army and took over Hueco Mundo in preparation for their war against Soul Society. He defeated Las Noches' new ruler, Tier Harribel, and took her as a prisoner to the Vandenreich's headquarters.
After sending Luders Friegen to Soul Society to make a formal declaration of war, Yhwach hastily leads an invasion force into Soul Society, ignoring the five day ultimatum he had Luders issue to Captain-Commander Yamamoto. During the invasion, Yhwach watches as Jugram Haschwalth killed Hidetomo Kajōmaru before giving Haschwalth explicit permission to leave the other members of the 13th Division alive if he saw it fit.
At some point during the invasion, Royd Lloyd replicates Yhwach's physical appearance and memories and takes his place on the front lines of the conflict. Posing as Yhwach, Royd defeats Kenpachi Zaraki but is killed in battle with Captain-Commander Yamamoto. After Royd's death, Yhwach arrives and finishes off the injured Yamamoto by slicing his body in half before incinerating the remains into oblivion. After giving an order to the soldiers of the Vandenreich to raze Soul Society to the ground, Yhwach is stunned by the arrival of Ichigo Kurosaki, who engages Yhwach in a brief conflict. Following his skirmish with Ichigo, Yhwach is forced to retreat back to the Vandenreich's headquarters, as his time outside of the "Schatten Bereich" is over.
Yhwach later announces the arrival of Uryu Ishida to the members of the Vandenreich and names Ishida his successor, much to the Stern Ritter's confusion and dismay. Later, Yhwach tells Ishida that he named him his successor in order to restrict his movements and keep the Vandenreich's focus on him, preventing him from formulating plans against them in secret.