In Sailor Moon R, Rubeus arrived from the future in a spaceship to find Rini (Chibiusa), who had also traveled into the past. His four servants were the Four Phantom Sisters (Ayakashi Sisters in the Japanese), named Catzi, Bertie, Avery, and Prizma (in the Japanese, they were called Koan, Berthier, Calaveras, and Petz, respectively), and continued sending them to find Rini, take over crystal points in Tokyo, and destroy Sailor Moon. However, Sailor Moon eventually turned them good, so Rubeus "evens the score" by capturing the other Sailor Scouts and telling Sailor Moon to hand Rini over. Sailor Moon goes to face him, and Rini comes with her. Rubeus takes them both into his ship and goes into space with it, and fights Sailor Moon using a power amplifier to adjust the gravity of the ship. Sailor Moon is able to stand at maximum gravity and fight Rubeus with Moon Scepter Elimination (referring to it as "Activation" rather than "Elimination" during the battle). While he is fighting her, Rini tries to break his power amplifier. Rubeus tries to stop her but Sailor Moon attacks him again, and he is forced to fight back with his energy blast, while Rini breaks the power amplifier, causing him to lose all his power and he is hit by the Moon Scepter Elimination beam, freeing the other Sailor Scouts.
Rubeus sets his ship to selfdestruct, saying it would be a great honor for the Sailor Scouts to go down with him and his ship. However, the Sailor Scouts were able to teleport out with Rini. Afterward, Emerald appeared. He asked her to take him back to the future, but Emerald is just there to make fun of him and tell him that he has failed all three of his missions (destroy the Sailor Scouts, find Rini, and get the Emperium Silver Crystal), hence the title of the episode, Rubeus Strikes Out. She then teleports away, deliberately leaving him to die as the ship explodes. When she informed Prince Diamond (who was going to kick him out if he didn't complete his mission soon) about his death, she omitted the fact that she left him for dead.
Rubeus can throw dark energy balls, teleport, and shoot beams of dark energy. If his power amplifier is destroyed, he loses all his power.
- Rubeus looks like Colonel Silver from Dragonball in the Red Ribbon Saga.
- Rubeus's English and Japanese names are closer than those of Emerald, Sapphire, and Diamond.
- When Wiseman tells Diamond "Do say hello to Sapphire and Emerald for me" he doesn't mention Rubeus at all (possibly because it was Wiseman who killed Sapphire, and had a major part to play in Emerald's death).
- Rubeus's death scene is similar to that of Evil General Durahan in the underrated anime Monster Rancher. Both are defeated by a major character in a beam struggle on a ship, which inevitably explodes. In the process, something important to them is broken in half (Rubeus's power amplifier and Durahan's sword). The heroes all teleport out and Rubeus and Durahan both have a confrontation with a female villain before the ship explodes (except in Durahan's case, he kills Lilim before dying in the explosion). Also, the episodes signal their doom: Rubeus Strikes Out, and End of Durahan.
- Rubeus is one of three Sailor Moon R villains whose name is similar to a character on Harry Potter, in his case, Hagrid, who shares the same first name. The other two are Bertie and Avery.
Voiced by Rob Tinkler in the English anime.