How do you get Ultimate Keyblade in Kingdom Hearts 1?

The Mythril Gem recipe isn't something you can find in the game Kingdom Hearts 2. It is automatically unlocked when you reach Moogle Synthesis level 8 under Free Development. To level up your Moogle Synthesis, create different items and using Bright materials (like Bright Shard, Bright Stone, Bright Gem, and Bright Crystal) will double the EXP when creating an item.