Something

Something is a force first introduced introduced in Kingdom Hearts Oblivion. The Something is a force that could be considered parallel to the Nothing. While, like all other forces, Something has probably always existed, its first recorded discovery was during the tests of The Inquisition on the human heart. When the Inquisition stripped the human heart of both Light and Darkness during their tests, they presumed there would be nothing left but a hollow shell. This, in fact, left Something in the heart of that person, and often resulted in transforming them into Hollow.

There are many theories to what the Something could actually be. One states that it is the force behind Light and Darkness, unseen until both are stripped away. Others say it only manifests in places where there is no Light or Darkness. One thing is known, however: it is extremely dangerous and uncontrollable, and is essentially the source of the Hollow.

Something can very easily be mistaken for nothing, and the only way to tell the difference is through the Sixth Sense, an ability all people have to 'fell with their hearts.' While Nothing cannot be detected with the Sixth Sense, Something can. Therefore, it exists.

When a person's heart is stripped of both Light and Dark, or anything else, Something manifests in their heart. The Something will then eat away at the person's heart until there is no heart left, and will proceed to 'inhabit' the person's body. This transforms the person into a Hollow. There is no known host whom has survived the 'inhabitation' process of the Something. All hosts transformed into Hollow.

Realm of Something
Since the discovery of Something, it has been widely assumed that there exists a Realm of Something. There is no true proof of this mythical place, but the myth says that at the end of the Realm of Something lies a door to Kingdom Hearts. According to the myth, the Realm of Something exists 'under' the Realms of Light and Dark, like a second layer of Universe waiting to be explored. Despite all these speculations, nobody has any way of reaching the Realm of Something. The most widely known theory is that of the Wormholes. Wormholes could also be referred to as cracks in the fabric of Spacetime. Through the Wormholes, people would be able to venture beyond the known Universe, into the fabled Realm of Something.

It is these myths of the Realm of Something and the door to Kingdom Hearts which would later inspire The Dark Empress to find a way in, and to transpire with the Hollow, in her bid to take over the Universe.