Darkling

The Black Costume is a Heartless created by Player who has fallen to the darkness. It is still able to speak simple sentences, access the Lanes between and fight without drawing power from the Book of Prophecies' fragments.

Kingdom Hearts χ[chi]
When the Player and Skuld reach the clock tower surroundings in Daybreak Town, they are surprised by a group of Black Costumes who attack them for their Lux.