Unversed

The Unversed are dark creatures and serve as the main enemies in Kingdom Hearts: Birth by Sleep.

They are creatures that are created from negative emotions from people, being created by Vanitas, who is technically the very first Unversed. They are very similar to the Heartless, but instead of being the manifested darkness of people's hearts, they are made entirely of the raw darkness created by the negative emtoions of people. The Unversed also do not seem to be interested in stealing the hearts of anyone they encounter, but seem to delight in attacking other beings and wreaking havoc on the worlds for the sole purpose of causing trouble.

As the Unversed can only come into being when a person's darkness is extracted from their heart and made into a real person, as long as Vanitas is alive, the Unversed can never truly be wiped out. Each Unversed that was destroyed had its negative energy sent right back to Vanitas, where he would simply revive it. This never-ending cycle continued until Ventus and Vanitas clashed at the Keyblade Graveyard. When Vanitas died, so did the Unversed.

Vanitas created the Unversed to draw Ventus and Terra out of The Land of Departure and provide enemies that would give them experience.