Forces

"But where there is light, darkness also lurks."

- Ansem the Wise, Secret Ansem's Report 1.

The Forces (勢力, Seiryoku) are the three primordial aspects of the realms: Light, Darkness and Nothingness. They appear in all forms, whether they be obvious or not. Their exact nature still eludes even the greatest minds, and much research has been undertaken in order to understand their true nature.

Wielders of the Keyblade are considered the guardians to the balance between Light and Darkness. Nothingness does not appear to be known to many besides Nobodies, who are the only beings capable of harnessing the even more ubiquitous force.

Light
Light is the most abundant force within the realms, and exists in every Heart along with Darkness. It is considered to be the force of "good" within the universe, but there are occasions when those of Light are considered to be malevolent. This is particularly evident by those who bear antagonistic thoughts towards the very existence of the darkness.

In the same vein as the other Forces, little is truly known about Light. Statements from various researchers have concluded that the original was the source of all light and a component of the. The light strongly resonates with positive emotions and may strengthen a Heart's resistance against ulterior forces.

There are seven individuals in the world who possess a Heart of pure light, known as the. In addition, the light in the hearts of children is said to be very pure, to the point where they managed to rescue the worlds from complete darkness, but forced their isolation to prevent further contamination from the darkness.

In the days prior to the, individuals had the ability to cross through worlds using Corridors of Light. As the light faded however, this ability has since been lost even among skilled Keyblade Masters.

Darkness
Darkness is the force parallel to Light. It is considered to be the product of light by those who have studied it, and all things inevitably switch between both forces, with the exception of the Princesses of Heart. Much like its counterpart, it is a force that comprises the original χ-blade.

The Darkness is, on the surface, an agent of corruption. Those who expose themselves to the Darkness will have their Hearts lost, and cause the creation of Heartless. This presents itself within abilities such as Magic as well, where classic elemental spells such as can possess "Dark" variants that are significantly augmented in strength.

Although believed to be malevolent, not all individuals use Darkness for malevolent reasons. For example,  is wielded by King Mickey and is the chosen Keyblade wielder for the Realm of Darkness, despite fighting for the light.

The Lanes Between worlds are those that are exceedingly close to the Realm of Darkness. As a result, those who travel them must wear specific protective equipment to avoid its corrupting influence, lest they fall into darkness.

Nothingness
Nothingness is an obscure force within the World. Although it technically exists, it is a force that gains its presence from Nobodies, beings that, for all intents and purposes, should not exist. It exists in a separate, but intertwined category with Light and Darkness for it makes use of them both simultaneously.

Nobodies are an existence that solely make up the Body and Soul. Their lack of heart means that they are capable of accepting any and all forces to empower themselves and gain an existence noticed by others: in other words, both light and darkness can be used to empower them. As a result, their powers are ubiquitous and varied, to the point where they can manipulate Heartless and travel through Corridors of Darkness but be unaffected by its corroding influence as a result of their unique state.

Due to the rarity of obtaining the power to wield Nothingness, it is not well-explored by those familiar with light or darkness, making its known limits difficult to establish.

Relationship with the Worlds
The World is made up of three realms: Light, Darkness and the Realm Between. These realms possess individual Worlds, and their characteristics can be altered by the forces they are surrounded with. Given that all worlds possess Hearts, it is very possible for a World of Light to fall into Darkness, or a World of Darkness to be closed and return to the Light. The exact circumstances behind the changes between worlds travelling through realms isn't fully known, although worlds that have been sent to the Realm of Darkness appear to be significantly distorted from their original appearance, unless they originated from Darkness.

Relationship with the Heart
All Hearts, from those of the people, to those of Worlds, possess an alignment to Light or Darkness. It is believed that the Heart itself gave rise to the Light, but that very Heart gave rise to the Darkness as others began to covet the Light and take it for themselves. Nonetheless, much like the Heart itself, the relationship between Light, Darkness and the Heart is left in obscurity, Though, it should be noted, Hearts appear to have some level of basis as "data", and they can be manipulated through the efforts of a Keyblade Master.