According to Sapphire in Episode 29, Rubeus "came crying to him after each of his lame attempts", and Sapphire did not want Emerald to do the same. He provided her with dark wedges to fill Tokyo's vulnerable spots with dark energy.
Sapphire was very suspicious of Wiseman, as he seemed to be egging Diamond on into putting new energy into the dark crystal's reactor, and Diamond did not realize that it could explode at any minute. Sapphire and Emerald tried to warn him, but he seemed to ignore them, as he was in love with Sailor Moon, which annoyed Sapphire and made Emerald jealous.
After Wiseman brought about the death of Emerald, Sapphire suspected his role in it. Once they entered the past, Sapphire overheard Wiseman saying he wanted to kill him and his older brother, and that he was working for the Doom Phantom. Sapphire took the control chip from the dark crystal's reactor to prevent him from detonating it. As he was about to go warn Diamond of Wiseman's treachery, Wiseman shot him with an energy beam. He was able to teleport away, but was injured by it.
He was later discovered by the Negamoon Sisters and taken into their house to heal. It was revealed by Avery that Prizma was in love with Sapphire. Sapphire began to realize that what Wiseman had planned was wrong. Prizma was sure that Wiseman would kill Sapphire if he tried to warn Diamond about him, so Catzi called Serena and asked her and the other Sailor Scouts to defend Sapphire from Wiseman and Wicked Lady. They were able to fight off Wicked Lady with the arrival of Tuxedo Mask. Diamond did not believe Sapphire, but eventually was willing to listen to him when Tuxedo Mask asked him. However, before Sapphire could tell his older brother Diamond about the Death Phantom's villainous plan, the Death Phantom appeared and killed him with an energy blast, leaving his older brother Diamond horrified. As Sapphire mentioned the Doom Phantom, Wiseman, ignoring a direct order from Diamond, blasted Sapphire again, this time killing him.
After his death at the hands of the Death Phantom, the bandages fell off his head, revealing that the crescent moon on his forehead had vanished.
- Prince Diamond (older brother)
- Unnamed father (deceased)
- Unnamed mother (deceased)
Unlike his older brother, Sapphire is never seen using any attacks in the anime, so it is unknown what his attacks are. It can be assumed that, like Rubeus and Emerald, he can shoot dark energy bolts, or energy waves like his older brother.
- Sapphire is the second villain to turn good and die in the same episode. The first is Neflite.
- Interestingly enough, both of their main jackets were removed before their deaths.
- Sapphire is the first of the major villains (that isn't a main or final antagonist) in the entire series that never sends any monsters of the week. Indeed, he never even comes up with any evil plans; as the series neared its end, by the time Emerald was killed, Sapphire became nothing more than a disposable villain (even though he turned good at the end). This was later repeated with the Witches 5 in Sailor Moon S, starting from Telulu (though each of them did get to try one evil plan for one episode, and none turned good before their deaths).
- Aside from his hair being dark blue, Sapphire looks similar in appearance to Darien.
Voiced by Lyon Smith