Soul King

The is the ruler of Soul Society, whose existence in Soul Society is as symbolic as it is absolute. He resides in the Soul King Palace and is protected by the Royal Guard. The Soul King is the father of Yhwach.

Appearance
The Soul King is humanoid in physique, with slicked-back dark hair, oval eyes and very thin eyebrows. His eyes are very unusual, consisting of four black circles which can change alignment. He does not have any arms or legs beyond short stumps. The Soul King exists within an unusual barrier that is framed on either side by bright white curtains as the focus point of a large, elegant room.

Purpose and Duties
The Soul King's sole purpose is to regulate the flow of souls into and out of Soul Society and keep the flow stable. Without the Soul King, the balance is lost and everything that is linked to Soul Society or made in it, as well as the Dangai, Hueco Mundo and the Human World will fall apart. According to a conversation between Kisuke Urahara and Sōsuke Aizen the Soul King is detailed as both a "thing" and "it". Urahara details that without the Soul King's existence, Soul Society would be rent asunder. The Soul King is the "linchpin" and if that linchpin is lost, then the world would simply crumble away and that is the way of the world.

The Soul King is not involved in governing Soul Society, having given the full control of its government to the Central 46 and thus being uninvolved with the day-to-day affairs of Soul Society.

History
At some point in time, the Soul King bestowed the title of "Monk Who Calls the Real Name" upon Ichibē Hyōsube. At some point, he also had restraints placed on his powers by the Shinigami.

The Thousand-Year Blood War arc
Shortly after the Royal Guard travel to the Seireitei and retrieve Ichigo Kurosaki and his Shinigami friends so they can heal and train in the Soul King Palace, the Soul King is approached by a retainer, who watches over the Soul King and inquires if he has awoken when the Soul King opens his eyes. A few days later, Yhwach, his son, arrives at the Soul King Palace and proceeds to slaughter many of the Soul King's vassals and subjects before arriving in the Soul King's room and stabbing him through the chest.

Soon afterward, Ichigo and his friends arrive in the room, where Yhwach reveals the Soul King's situation to them before claiming they are too late to do anything. When Ichigo attempts to help the king by pulling out Yhwach's sword, Blut Vene veins spread over his right side and force him to slash the Soul King across the torso. Yhwach explains Ichigo's actions by revealing that Quincy blood cannot tolerate the Soul King's existence.

As the lower half of the Soul King's body and containment pod fall to the ground, Yhwach explains to Ichigo how he forced Ichigo to attack him by giving the Reiatsu still present in his sword to him, which his blood reacted to. When Orihime attempts to revive the Soul King, her Sōten Kisshun shatters, prompting Yhwach to proclaim that the Soul King will never rise again.

However, in the Seireitei below, Jūshirō Ukitake, who was once saved by Mimihagi, the right hand of the Soul King, initiates Kamikake to save the Soul King's life at the cost of his own. Upon doing so, a large black hand bursts out of his orifices and ascends toward the palace, where it grabs the upper half of the Soul King's body. Shocked by this, Yhwach notes that Mimihagi is the one thing that his eyes cannot predict and demands to know if the Soul King is beginning to feel sentimental toward Soul Society after protecting it for all this time as the eye on the hand of Kamikake begins to close.

Yhwach attempts to destroy both the Soul King and Mimihagi, but Ichigo stops him by grabbing his arm and dispelling his attack, allowing Yoruichi to leap past them and create a Kidō barrier around the Soul King with several seals. Yoruichi notes that Mimihagi has stabilized the king before proclaiming that they will have to replace him. However, when Yoruichi momentarily loses her concentration due to Uryū Ishida shooting her in the shoulder, the barrier shatters, sending the top half of the Soul King flying toward Yhwach, who rips Mimihagi off of it. After absorbing Mimihagi, Yhwach completely absorbs the Soul King.

Powers & Abilities
Immense Spiritual Power: As the supreme ruler of the Soul Society, the Soul King has an incomparably immense amount of Spiritual Power. When Yhwach, who possesses immense Reiryoku himself, absorbed the Soul King's full power, the Quincy Emperor collapsed from the sheer strain and needed some time for his body to fully acclimate to it. During this period, the Soul King's Reiatsu kept pouring out of Yhwach to such a degree it manifested as countless "shadow creatures" that threatened to destroy the Seireitei. A further testament to the Soul King's power is that even two of his severed body parts retained enough Reiryoku for Yhwach to acknowledge them as members of his personal guard, the Schutzstaffel.

Soul Regulation: The Soul King's sole purpose is to regulate the flow of souls in and out of Soul Society. Without his existence, all known dimensions connected to Soul Society will begin crumbling into non-existence.

Ōken Bestowment: The Soul King is capable of granting those whom he chooses as members of the Royal Guard with the Ōken, a special tool that allows one to enter the dimension of the Soul King Palace whenever they wish. The king achieves this by literally turning the bones of those he selects as Royal Guard members into this Ōken.

Precognition: Like his son, Yhwach, the Soul King has the ability to see into the future. Yhwach theorizes that the Soul King has seen all the events of the Quincy Blood War, up to and including him invading the Soul King Palace.

Weaknesses

 * Power Restraints: The Soul King has restraints placed upon his power by the Shinigami. Yhwach implies these restraints prevented the King from fleeing his death.

Sentient Body Parts
Various parts of the Soul King have been separated from the main body and attained sentience. They each have their own names, personalities, and abilities.

Trivia

 * In his first appearance in Chapter 519, the Soul King's silhouette appears to have arms and legs. In all subsequent appearances, his arms and legs are removed.
 * Pernida Parnkgjas and Gerard Valkyrie both identify as Quincy. When Mayuri Kurotsuchi confronts Pernida about this, the left arm asserts it has always been a Quincy.
 * Yhwach considers the Soul King's existence, a sealed and mutilated linchpin made to stabilize the Soul Society, unacceptable to the Quincy, and calls it a "humiliation". He also calls the Soul King Palace a "decaying grave". Anyone with Yhwach's blood is forced to end the Soul King.
 * According to Jugram Haschwalth, the Soul King's true enemy is the Shinigami. When released from the Shinigami's seal, a torrent of the Soul King's power attacks the Shinigami and ignores the nearby Quincy.
 * Despite this, Mimihagi aids the Shinigami, much to Yhwach's confusion. Yhwach speculates that the right arm has grown attached to the Soul Society after being worshiped as a god for so long.

Appearances in Other Media
In Bleach: Can't Fear Your Own World, the Soul King's Saketsu is revealed to be another one of his severed body parts, and incarnated itself in the Fullbringer Aura Michibane. Likewise, it is revealed by Ichibē Hyōsube that the Soul King predates Soul Society and that through the Soul King's powers, named The Almighty, Soul Society, the Human World, and Hueco Mundo were created out of a singular, primordial world.