Vanitas, also known as The Masked Boy, is a Keyblade wielder and the secondary antagonist of Kingdom Hearts Birth by Sleep. He is the second apprentice of Master Xehanort, the embodiment of the extracted darkness from Ventus's heart, and the source of the Unversed.
Vanitas's name is derived from the Latin word for "vanity" or "emptiness", and was chosen for its meaning, that it sounded similar to "Ventus", and that it was a written pun on "Sora" (空?, lit. "emptiness") in Japanese.
Vanitas joined the shadow force when etna told him about taking over the world. He was the one Etna trusted to look over Aster phoenix's test. He has more power than most of the shadow force, being higher in the ranks than Broly.
Vanitas and his master are both members of the Cosmic Empire.