AntiSora

The Anti-Sora was a shadow duplicate of Sora that Riku created merely to show his power of darkness to Sora. It appears in Kingdom Hearts, in the Neverland world. Several lesser, forms, such as Shadow Sora, takes the form of Sora's shadow, though capable of flight, they seemingly have weak stats, and drops a large amount of HP orbs upon being defeated.

Story
Anti-Sora was created upon Sora and gang's visit to Neverland. There, Sora 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 completely black. Sora encounters Shadow Soras, enemies similar to Anti-Sora, countless times throughout his adventure on Captain Hook's ship, although it has no weapons and disappears before he can destroy it.

Anti-Sora (excluding the boss fight) only taunts Sora and his other party members during the travel before your boss fight with him. If you are able to "beat" these clones, they will drop a bundle of magic orbs and certain items. The clones also, may only be attacked by Sora and no one else throughout the ship. After you defeat the main Anti-Sora, the clones stop appearing.

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

When Sora defeats it, Anti-Sora falls back into darkness. It drops the Raven's Claw.

Trivia
Anti-Sora is also a form Sora can use in Kingdom Hearts II and is activated by using forms too much.