Kingdom Hearts, also known as The Heart of All Worlds and The Sacred Moon, is a major object and location in the OE universe. It is a creation made of all lost Hearts. There are two different Kingdom Hearts: one in the Dark Realm and one in the Realm of In-Between.
Heart of All Worlds Edit
Kingdom Hearts is the Heart of all worlds, the main goal of all Heartless. It is here that Hearts are born, and when Hearts are lost, they return here. Even the Hearts of worlds are collected here if the Heartless reach them. When Hearts return to Kingdom Hearts, they become one with it, melding into it to form a "solid" mass.
Light within the Darkness Edit
Though all Hearts have the potential for both Light and Darkness, Kingdom Hearts, like all Hearts, is inherently Light. So potent is the Light from so many Hearts that Kingdom Hearts can instantly annihilate any Heartless that comes into contact with it, and the Heart it contains is consumed.
However, Kingdom Hearts naturally resides in possibly the deepest part of the Realm of Darkness. The Darkness and Light are drawn to one another, so the only way to reach the Light of Kingdom Hearts is to traverse immense Darkness. The Kingdom Hearts that resides in the Realm of In-Between draws millions of Heartless onto the world, making it one of the most dangerous places to travel for a being with a Heart.
Kingdom Hearts II Edit
The second Kingdom Hearts is in fact simply a replica of the real one. Created by Organization XIII, Kingdom Hearts II appears as a massive heart-shaped moon hovering over The World that Never Was, a world designed specifically to house Kingdom Hearts and the Nobodies attempting to create it.
It was made by, over the years, collecting Hearts from around the Realm of Light and keeping them together until they began to combine and draw in other loose Hearts. The work was slow, as they needed to destroy Heartless and release their Hearts to do so - a hard task without the help of a Keyblade. Eventually, however, they were able to use the power of the Keyblade and nearly completed it. At the last moment, however, Ansem the Wise destroyed it, completely ruining 10 years worth of work. What was left of it, Xemnas absorbed and used to become supremely powerful, but was defeated.
Euphoria of Hearts Edit
Many Nobodies claim they can hear Hearts, and that Kingdom Hearts often sounds like a soft yet joyous singing.