Yes, the Blue Gear only spawns on Mirage Island and only appears at night. You’ll need this key item to upgrade your race to V4, also known as “Race Awakening.” To complete the “Race Awakening,” you also need to bring a Mirror Fractal to the island and find its highest point. From there, look at the moon for about 15 seconds until a message appears. You can then scour the island to find the Blue Gear.