Kingdom Key D

This alternate version of the Kingdom Key is called the Keyblade of the Realm of Darkness and, among fans, referred to as the Kingblade or the Inverse Kingdom Key. The Keyblade of the Realm of Darkness was found in the Realm of Darkness. Since the Keyblade of the Realm of Darkness is a reverse colorization of the Kingdom Key, it is believed that these two are the original Keyblades.

It wasn't the King's since before Kingdom Hearts. In fact, he previously wielded the Keyblade Star Seeker, as shown with King Mickey wielding it in Birth By Sleep when he was still an apprentice of Master Yen Sid. This Keyblade was shown in the secret ending of Kingdom Hearts II called The Gathering, along with Sora's Kingdom Key and Riku's Way to the Dawn. These three Keyblades, along with Master Xehanort's keyblade, are the only ones shown with Keychains.

It's unkown exactly how the King obtained the Keyblade of the Realm of Darkness. It is interesting to note that the Keyblade is very much an anti to Mickey's Light personality.

In Kingdom Hearts II, he is not shown wielding any weapon, except the Keyblade of the Realm of Darkness and his hilarious wits in Timeless River.

It was originally seen in the closing video for Kingdom Hearts. It is expected to appear in Kingdom Hearts coded.