Heartless

Heartless
The Heartless (ハートレス Hātoresu?) are beings of darkness that manifest in two forms, "Pureblood" and "Emblem". While most Heartless are in fact manifested hearts, they behave entirely devoid of emotion, and thus were named "Heartless".

The Heartless are the primary enemy type in the Kingdom Hearts series, with various subspecies appearing as enemies in every game.

Story
Keyblade wielders fight both Pureblood and Emblem Heartless as they journey across the worlds to collect Lux. However, these are merely projections from the Book of Prophecies which contains records of future events, as true Emblem Heartless did not yet exist.

Design
In general, Heartless are beastly creatures with beady yellow eyes.

As naturally occurring Heartless, Pureblood Heartless look more primitive and tend to use more chaotic fighting styles. When they are not possessing objects or using them as armor, Pureblood Heartless are predominantly dark-toned with eerily-colored veins, antennae, and tendrils on their bodies. Some Pureblood Heartless have chains hanging off their bodies. Particularly strong Pureblood Heartless look somewhat humanoid and possess a heart-shaped hole in the center of their torso.

Emblem Heartless have more varied shapes and colors than their Pureblood cousins. They are also branded with Xehanort's emblem to differentiate them from the Pureblood ones. The Heartless emblem resembles a heart with a fleur-de-lis at the bottom and a spiky "X" crossing through the center.

They possess unique abilities, for example, the Leechgrave uses its tentacles to eat other Heartless. When the Marionette possesses toys, the Heartless emblem appears on them.

Nature
Pureblood Heartless are natural Heartless, born from the darkness in people's hearts. They are more common in places that are close to or saturated in darkness. Upon their destruction, they simply disappear in puffs of darkness, without a heart leaving its body. While Purebloods have less variety, they are far more numerous in quantity and often attack in swarms.

Emblem Heartless, on the other hand, were originally created from a machine designed to reproduce the process of a heart being consumed by darkness. Once that machine was activated, most stolen hearts become Emblems, provided they contain darkness. They are more common on the worlds within the Realm of Light, and usually mimic the shape of creatures or objects within that world. The machine fell into disuse after Kingdom Hearts, due to the Villains losing the control of Hollow Bastion. However, powerful Emblem Heartless have also been shown to be created directly from a dragon from the Land of Dragons, Prince Hans and Mother Gothel.

Heartless – Emblem or Pureblood – possess several key characteristics that define them as Heartless. Pureblood Heartless are generated naturally from the darkness within people's hearts. Heartless are born when a heart is consumed by the darkness within it, or when a Heartless steals the heart. They can also be drawn out by a dark being like Maleficent or a source of dark power like the Keyblade of heart. This process will occasionally also form Nobodies, which are born from the body and soul left behind when the heart is lost. Being born from darkness, they are mindless and act on instinct; because of such, their only goal is stealing more hearts to turn into Heartless. But what they desire above all are the hearts of worlds, and thus they enter worlds in search of the way into the hearts of the worlds. When they consume these colossal hearts, the remains of the world form new worlds, such as Traverse Town and End of the World.

A Soldier, an Emblem Heartless.

At the same time, Heartless seek out the users of the Keyblade, since the Keyblade holds the power to lock and unlock hearts. If a Heartless is slain by a Keyblade, it will reunite with the body and soul it left behind, if it isn't currently a Nobody. In order to stop the users of the Keyblades, the Heartless use the Keyblade itself as a homing beacon, but ultimately desire to take the heart that commands it. Because of this, Keyblade wielders are under constant attack. Magic can also destroy Heartless, but only temporarily.

The strength of a Heartless is proportional to the depth of the darkness from which it was born. The darker the heart forming a Heartless, Emblem or Pureblood, the more powerful and more monstrous the resulting being will be. An exception to this is Xehanort's Heartless, who retained his human appearance for unknown reasons. This is a contrast to Nobodies, which determine rank according to the strength of the heart, and whose appearances become more human as they increase in power. Furthermore, as beings of elemental darkness, some Heartless are able to take possession of other beings or even inanimate objects, granting them immense dark power and often reshaping their very forms to suit their purpose.

The Heartless, being mindless, usually have no master to direct their actions and instead act on the instinct to consume more hearts. However, there are some higher beings who can command them. Heartless will obey those with an affinity for darkness and a strong will. If many people attempt to control them, the Heartless will side with whomever is most powerful. However, those with hearts, such as Maleficent, endanger themselves, as the Heartless are attracted to their hearts and if they show weakness, the Heartless will not hesitate to consume their hearts.

On the other hand, higher ranking Heartless, like Xehanort's Heartless, can fully command other Heartless without endangering themselves. Also, Organization XIII is able to command them as well with their strong wills, but are not endangered of being consumed by them for their lack of a heart.

Heartless make use of the "Corridors of Darkness", inter-dimensional pathways that connect the many worlds. These pathways are located in the Realm of Darkness, and thus are very dangerous to use if one is not accustomed to the darkness.

The Heartless invasion

 * "Your past endeavors did prevent an immense effusion of Heartless from the great darkness; make no mistake about that. However, the Heartless are darkness made real---and darkness lingers yet in every heart. The Heartless are fewer. But while darkness exists in a single heart, it will be difficult to eliminate them."
 * —Yen Sid

While the Heartless were not researched with the intent of creating a fighting force, their very nature as manifestations of the destructive force of darkness made them naturally suited for conquering and destroying the various worlds. Their natural ability to travel to various worlds through the use of Corridors of Darkness makes it virtually impossible to fully defend a world from Heartless, and the method in which they are created and exist makes it practically impossible to cut them off at the source. Even fighting them once they appear is made difficult due to their immunity to standard weaponry.

According to the Ansem's Reports, a Keyblade can lock the heart of a world away from the Heartless forever. However, this does not keep the Heartless out of the world; it simply prevents them from destroying it. The citizens of the worlds remain fair game to the Heartless. Although the Door to Darkness was sealed, the Heartless continue to exist naturally in fewer numbers due to the darkness still existing in people's hearts. However, evil beings such as Pete and Organization XIII seek to create abnormally strong Heartless by forcing beings with strong hearts to succumb to darkness. Thus increasing the threat the Heartless pose.

The primary weapon for destroying the Heartless is the Keyblade, as it is both specially suited for manipulating the bonds between heart, body, and soul which create Heartless, and it is the only object able to thwart the Heartless in their goal of devouring a world's heart. However, in the absence of the Keyblade there are several other options. Magic is effective against the Heartless, as are magical weapons. In either situation, invading Heartless can be made disorganized by defeating the major Heartless which leads them, or the dark heart which attracted them to that world. While this does not by any means purge the world of its Heartless, it gives no small respite from their threat. Emblem Heartless that are destroyed by a Keyblade release the heart within them, sending it to a Kingdom Hearts where it waits for its body and soul to be freed, so that the person it once was can be woken once again.