|“||I always get everything I want. Everything.||„|
|~ Prince Diamond|
|“||Don't underestimate me!||„|
|~ Prince Demande while trying to finish off Wiseman|
Prince Diamond, also known as Prince Demand (プリンス・デマンド, Purinsu Demando, Prince Diamond in the English dub) is the leader of the Black Moon Clan.
As the founding leader of the Black Moon, Prince Demande saw the Crystal Tokyo and the reign of Neo Queen Serenity as an ambition duel to the Legendary Silver Crystal prolonging human like by a millennia. Demande and his followers were lured by Wiseman to Nemesis where they acquired the power of the Malefic Black Crystal. While the plan was to travel back in back to kill Neo Queen Serenity when she was Usagi Tsukino, Demand acted rash to directly attack Crystal Tower by sending a Black Crystal fragment large enough to level the city. It was then that Demand encountered Neo-Queen Serenity while she was looking her daughter Chibiusa, becoming obsessed with her from both her glare and witnessing the Legendary Silver Crystal's power before hand.
This obsession included Usagi whom Demand abducted when she traveled from her time to 30th century Japan. Demand held her in Black Moon Castle before she managed to escape with her friends as the palace collapsed when the Malefic Black Crystal Reactor underwent a melt down. Prince Demande then realizes he was simply being used by Wiseman and revolted against him after feigning to have fallen under his control, forced to kill his own brother while unmasking Wiseman as Nemesis itself. The latter act drove Demand insane, stealing the two Silver Crystals from Black Lady and nearly causing the destruction of space-time continuum were it not for Sailor Pluto's intervention. While the manga has Demand die fighting Sailor Moon and Tuxedo Mask, Sailor Moon Crystal depicts him sacrificing his life to shield them from Wiseman's attack.
He was manipulated by Wiseman into attacking Crystal Tokyo and taking over the Earth. Finding Crystal Palace to be invincible, he sent one of his commanders, Rubeus, to the past to take over Tokyo by securing crystal points. However, Rubeus's plans were all foiled by Sailor Moon, and after his death, Diamond sent Emerald into the past to carry out her plan of taking over Tokyo by filling its vulnerable spots with dark energy. After several failed attempts, Diamond called her back.
Diamond is in love with Sailor Moon, and when she and the other Sailor Scouts went with Rini to the future, Diamond tried to hypnotize her into loving him, but Tuxedo Mask stopped him. After Emerald was destroyed, Diamond, Sapphire, Wiseman, and Wicked Lady (Rini brainwashed by Wiseman) traveled to the past and placed a dark crystal in the middle of Tokyo. Diamond's younger brother Sapphire discovered that Wiseman was conspiring against them, and tried to warn him, but was killed by Wiseman. Diamond was angry at Wiseman for this, but didn't believe Sapphire at first.
Sailor Moon came face to face with Diamond inside this crystal, where he unsuccessfully tried to hypnotize her. Soon, he realized that Sapphire was right about Wiseman, and fought him. Wiseman directed a dark spear attack at Sailor Moon, but Diamond jumped in front of her and took the hit. Though he managed to destroy Wiseman's arms (Wiseman came back together), he died from his injuries.
Demand can shoot energy waves and energy balls (not unlike Dragonball Z style attacks). He also possesses the ability Evil Sight, opening a third eye on his forehead that allows him to hypnotize or psychically immobilize his opponent.
- HIs original voice actor Kaneto Shiozawa also voiced Devimon. His voice actor in Sailor Moon Crystal, Mamoru Miyano, voiced Light Yagami, Shuu Tsukiyama, Abidos the Third, Chrollo Lucilfer, Berg Katse (Crowds), and Ferocious Knight D.
- His English voice actor in the Viz version and Sailor Moon Crystal, Matthew Mercer, voiced Reapmon.