Ryuax was a Droid belonging to Esmeraude that appeared in episode 82. She was charged with the mission of finding Chibiusa and bringing her alive to Prince Dimande. Ryuax's personality was generally cool and calculated. She assumed the form of Neo-Queen Serenity to lure Chibiusa to her, but Chibiusa was alerted to the trick because Ryuax called her "Rabbit."

She was able to attack with her hair and also had the ability to reverse the flow of time, causing any attacks by the Sailor Senshi to be returned to them. Using her Mercury Goggle, Sailor Mercury determined that after Ryuax used her powers, there was a distortion in time in which the Senshi could attack her. Chibiusa volunteered to bait Ryaux and she was saved from Ryuax's counter-attack by Tuxedo Mask. The Senshi then defeated her with Sailor Planet Attack.

Ryaux's vocal attack was called "Ryuax Power."