Prince Diamond (Prince Demand in the Japanese and manga) is the leader of the Negamoon, and one of the two main antagonists of Sailor Moon R (the other being Wiseman).
In the anime
Neo Queen Serenity banished him to the Negamoon for refusing the purification she offered, and since then he has been seeking revenge, though he is in love with her.
He first sent Rubeus into the past, but Rubeus was defeated by the Sailor Scouts, and destroyed along with his ship. Emerald was then sent into the past, but the Sailor Scouts kept foiling her plans. Emerald was in love with Prince Diamond. After her death, Diamond's younger brother Sapphire found out that Wiseman was only using them for his own twisted goals, and attempted to warn him, but was killed by Wiseman.
Shortly after, in Episode 83 (original airing) or 76 (English subtitled), Legend of the Negamoon, Diamond attempted to hypnotize Sailor Moon, but eventually turned on Wiseman, now fully aware of his intentions. When Wiseman directed two dark energy blades at Sailor Moon, Diamond jumped in front of her and took the hit, and died as a result of this injury. However, he was able to damage Wiseman, shattering his arms, but Wiseman came back together.
Diamond can shoot energy waves from his hands, and also hypnotize others using the third eye on his head, which rarely opens.
- The character Princess Diamond from Episode 18, Worth A Princess's Ransom, has a similar name and title to Prince Diamond (a princess as opposed to a prince), but they are entirely unrelated to each other.
- The way Prince Diamond dies is similar to Harry Osborn from Spiderman 3. Both sacrifice themselves to save the main character from two blades heading straight at them.
Voiced by Robert Bockstael in the English anime