Atelier Iris 3: Grand Phantasm Cheats

After you completed every quest, the last quest "Truth in Darkness" will be reveal on the board at the Guild. After complete "Truth in Darkness" quest, then create the Shadow Gem by using the item synthesis on Ruby Prism (from another item synthesis on Aroma Material, Brilliant Stone, Dunkelhite and Dragon Tongue) and Broken Gem (which you got from the "Truth in Darkness" quest. And last, go face the final boss Uroboros and beat him to see the True Ending.