Heartless (KH: CotS)

The Heartless (ハートレス) are beings of darkness which manifest in two forms, "Pureblood" and "Emblem". While most Heartless are in fact manifest hearts, they behave entirely devoid of emotion, and were thus named "Heartless". The Heartless appear once again in Kingdom Hearts: Child of the Sun as an enemy to Galexgan and friends.

Story
The Heartless are once again active in Kingdom Hearts: Child of the Sun. The New Organization tries to gain hearts from the Heartless without a keyblade, they also study the Heartless to find easier ways to defeat them.

End of the World and Kingdom Hearts
The Heartless reside wherever darkness is abundant, especially the Realm of Darkness. However, they also reside in places such as the End of the World, a collection of the remnants of worlds that is located near the darkness. Another area that the Heartless live in is The World That Never Was, the world of the Nobodies that rests dangerously close to the darkness upon which the Heartless thrive.

Heartless, as they seek and consume hearts, also desire to return to the greatest heart, the heart of all worlds, Kingdom Hearts, that resides deep within the Realm of Darkness. And because of this, Heartless seek immense darkness, enough to completely consume the Realm of Light. The entryway into this place of great power is the Door to Darkness, the door that separates the realm of light and the realm of darkness. However, with the efforts of Sora and the King, the door is closed, which causes the worlds lost to the darkness to be restored, and preventing a massive army of Heartless from pouring into the realm of light.

The forces of the Heartless were extremely weakened after the door to Kingdom Hearts was sealed off, though there were still many left. At the end of Kingdom Hearts II, it is unknown what exactly happened to the Heartless and if they still pose a threat. It should be noted though that Yen Sid has mentioned that the only true way to destroy all Heartless is to have all people have light filled in their hearts and no darkness, leaving nothing to create a Heartless or something for them to thrive for.

Types
Note- A name in bold denotes a boss.

Gummi Heartless
Much of the information gathered for this article is gotten from the Kingdom Hearts Wikia.