Mon Amour Stone
From Starfy Wiki
The Monamool Stone (Japanese: モナムールストーン) is a large heart shaped gem in Amiy Palace belonging to the Amiy Kingdom. It is a mystical stone that was passed down in care as a protector of the Amiy Kingdom. The residents of the Amiy Kingdom lived happily in peace, guarded by the Monamool Stone.
In the events of Densetsu no Starfy 4, Dejiru stole the Monamool Stone to become more beautiful to Prince Coral, before turning Amiy Palace into a castle of her own. She also exploited its power to overlook Starfy and Starly on their adventures, and sent bosses to stop them on their paths.