This is the 34.5" Sora Keyblade Oblivion Officially Licensed Disney Kingdom Hearts Fantasy Sword constructed out of durable EVA Foam.

Oblivion is similar in shape to the Kingdom Key, though is black and has a longer reach. The hilt guard is comprised of two bat-like wings extending downward. The teeth are in the shape of the Kanji for "darkness".
The Keychain's token is a black version of Sora's crown necklace. A chain-like design runs up the length of the blade. The diamond in its hilt also resembles the diamond in the original logo of Hollow Bastion. When the Oblivion is summoned in Kingdom Hearts II, black smoke and violet sparks surround it.

The Keyblade's name means a "state of forgetting or having forgotten", and its Japanese name has the same basic meaning.