Ultima Weapon

Ultima Weapon is a form for Sora's keyblade in Kingdom Hearts and Kingdom Hearts II. In both games, it is synthesized by the Moogles, but the appearance and abilities are different for each game. In Kingdom Hearts it is the strongest Keyblade in terms of strength and MP, but in Kingdom Hearts II it is second in strength to Fenrir (tied with Oblivion and Decisive Pumpkin) and second in magic to Fatal Crest (tied with Bond of Flame.) In Kingdom Hearts II Final Mix+ it is third in magic to Winner's Proof.

Kingdom Hearts

 * 5 Lucid Gems
 * 5 Power Gems
 * 5 Thunder Gems
 * 3 Mystery Goo
 * 3 Gales

Kingdom Hearts: Final Mix

 * 5 Thunder Gems
 * 5 Mystery Goo
 * 3 Mystery Force
 * 3 Gales
 * 3 Dark Matter

Kingdom Hearts II
The Ultima Recipe can be found in the Basement.
 * 13 Orichalcum+
 * 5 Orichalcum
 * 1 Mythril Crystal
 * 1 Dense Crystal
 * 1 Twilight Crystal
 * 7 Serenity Crystals

An Energy Crystal is required to reduce the needed Orichalcum+, as there are only 7 in the game.

Design
The Ultima Weapon Keyblade is named after the sword of the same name in the Final Fantasy series. The Ultima Weapon is typically shown within the Final Fantasy series as a long sword, with a glowing blue/white blade and a golden handle. It is usually the strongest weapon for the protagonist in the games it appears in.

Trivia

 * If you look closely, you will notice that the Kingdom Hearts version appears to have the Dream Sword underneath the lacing.
 * In Kingdom Hearts II, through the use of an Action Replay, two extra Keyblades can be obtained, namely the Edge of Ultima, a palette swap of the Kingdom Hearts version of the Ultima Weapon, and the Detection Saber, a palette swap of the Kingdom Hearts II version of the Ultima Weapon. While accessing these Keyblades in Sora's Items menu, no picture of the Keyblades are shown - only map icons. This implies that these two Keyblades were removed from the game.