Ventus and Vanitas

"I've become a part their heart, just as they've become a part of mine. My friends are my power... and I'm theirs!"

—Ventus to Vanitas before their final battle

Ventus, also known as Ven, is one of the main protagonists in Kingdom Hearts Birth by Sleep. His name means "wind" in Latin, similar to how Sora's name is Japanese for "sky". He was a Keybladewielder before Sora ever became one, and was apprenticed to both Xehanort and Eraqus. He is the youngest of the trio formed by himself, Terra and Aqua.

Ventus's heart is severely damaged by the creation of his dark counterpart, Vanitas, and then again when the χ-blade forged from their hearts is destroyed. Both times, Sora's heart reaches out to mend Ventus's heart, and by the end of Kingdom Hearts Birth by Sleep, Ventus's heart has gone to sleep within Sora so that it can recover until it is fully healed and ready to rejoin his body, which lies comatose but safe within the Chamber of Waking. The official Japanese website refers to Ventus as the "Swift Wind Returning to Bonds" (絆巡る疾風 Kizuna Meguru Shippū^?).

"He has no control over the darkness in his heart. The Keyblade is not his to bear. He's an abomination beyond hope of salvation."

—Master Xehanort to Terra

Vanitas, also known as The Masked Boy, is a Keyblade wielder and one of the primary antagonists in 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.^[1]