Oblivion

The Oblivion is a Keyblade in Kingdom Hearts, gained by opening a chest located in the room where Riku was fought while possessed by Xehanort's Heartless. The player doesn't get a chance to open it until after the fight. One of the strongest melee-oriented Keyblades in the game. Oblivion reappears in Kingdom Hearts II, as both a key chain for Sora after his reunion with Riku, and as one half of Roxas' dual set of Keyblades, the other being Oathkeeper. It can be seen as a Keyblade of darkness, to balance out the light of Oathkeeper. The teeth are fashioned in the shape of the Kanji for "darkness" (闇), corresponding to the Oathkeeper's Kanji for "light". Also, the name is reminiscent of Castle Oblivion, and the design of the shaft looks like an Organization XIII robe.

In Kingdom Hearts: Chain of Memories, the Oblivion card is obtained on the 12th floor after completing Destiny Islands, and after defeating Larxene for the second time.

Appearance
Oblivion is similar in shape to the Kingdom Key, though is deep 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" (闇). The keychain motif is a black version of Sora's crown necklace.

Trivia

 * Oblivion is one of two keyblades weilded by Roxas during battle with Axel and during battle with Sora (Final Mix exclusive)

Tips
In using this keyblade, you can easily level up your Drive Gauge. It can also increase its effect in depleting your MP due to MP Charge