AntiSora

The Anti-Sora was a shadow being created by Riku. It was Heartless clone of Sora that he created merely to show his power of darkness to Sora. It was a boss in Never Land.

Story
Anti-Sora was created upon Sora and gang's visit to Never Land. There, he meets up with Riku, who tells him he now has power over the Heartless. To prove this, he summoned a shadow clone of Sora - Anti-Sora - that was somewhat similar to a Shadow, because its eyes were yellow but its body is completly black. Sora encounters the Anti-Sora countless times throughout his adventure on Captain Hook's ship, although it has no weapons and disppears before he can destroy it.

Sora makes to the captain's quarters, where Riku summons Anti-Sora to despose of Sora. There, it wielded a shadow-version of the Kingdom Key. Although, Magic was not available to it. It also could flatten itself and crawl beneath things like a Shadow.

When Sora defeats it, Anti-Sora falls into a black void that appears beneath it.