He is Prince of the Black Moon and one who willingly serves under and secretly follows the orders of his one true master, Wiseman. Saphir is his younger brother. Diamond wants to smash the Silver Crystal to pieces. He is the one who discovered the full, fearsome strength of the Evil Black Crystal.
Operation: Re-play. A rebirth of history.
Prince Demande has short white hair. He wears a white suit with a long purple cape. He has blue eyes and wears Black Crystal Earrings.
Prince Diamond has no use for the 30th Century Earth. He sends in troops to the past, before it was ruled by the Moon Kingdom, and destroy history. Then write a new chapter of Black Moon history.
He is destructive and always straying from plans on a sudden impulse. Even launching the Black Crystal into the Earth and turning it into a dead planet was not part of the original plan.
in Act 25 Prince Diamond protects Sailor Moon with his invincible evil sight from the Wiseman/Death Phantom, stating that he wants to be the one who kills her.
He is destroyed by Death Phantom