Regentium is a metal used to make weapons in Atelier Meruru: The Apprentice of Arland. Regentium is the highest quality ore and can create weapons that are level 9 and 10. If the player cannot synthesize Regentium, Sunlite can be used as an alternative. They can be used to craft the most powerful weapons in the game, utilizing the Rainbow Fragment's unique "rainbow power" trait.