Ruby Crescent (ルビィ・クレセント, Rubii Kuresento) is one of the main characters main character of O-Parts Hunter (aka 666 Satan.) Ruby is a young girl who travel the world to find O-Parts and her father. Ruby met Jio Freed on her journey and became friends with him. Her O-Parts is Jade Pendant.
Ruby Crescent is a young girl with straight blue hair with ponity tail. She has four little bells in her hair for display. In the post-Rock Bird she got taller and had more a woman body and wear a tank top, shorts, and boots.
Ruby almost always seen with a smile, because she says that after her father died, she realized that just crying and running away won't solve anything. She always worries about Jio and Ball when they are fighting against other O.P.Ts. Ruby shares a strong bond of friendship with the two, but seems to have more intimate feelings for Jio, whom she has known for a much longer time than Ball.
Ruby was seen in many different treasure hunter who is researching the mysterious, legendary O-Parts. She carries an extensive knowledge of ancient languages and her other objective is to uncover the mystery of her father Sect Crescent's death. She carries a necklace, which her father gave her and which is afterwards discovered to be the Jade Pendant, a S Rank O-Part with over 100 effects.
It is later revealed that she is the host of Sandalphon, the No. 10 Angel, along with the fact that her father is actually a traitor to the Stea government and not really her father, but just a man who was taking care of her until she awakened as the No. 10 Angel. Despite this she still considers him as her father. Her soul, pulled out from her body by Shin's fully powered Zoru, is absorbed into Jio at the end of the Olympia Arc when Satan is fighting Cross after the former receives a fatal wound. Post time-skip Jio and his friends fight their way into Stea's Capital and Jio is able to reverse the absorption effect and restore Ruby's soul into her body, kept in a big container where its real form could be seen. Ruby is a clone of cross's sister, lily.
She is now able to use her Angel powers, though they aren't complete. After Ruby is reunited with her father, the leader of Zenom, Zekuto Crescent, he claims to have no daughter, leaving Ruby distraught. After Jio arrives and saves the crew, Shin begins collecting all of the demons and angels, and later, even human's souls. Ruby takes the hit for her father and they both give a pinky promise, something Ruby refused to do many years before. Both were devoured by Shin, because Ruby was the host of an Angel and her father was the host of two demons, in order to make the Kabbalah complete.
Inside the Kabbalah, in order to save the world, she along with Jio, Cross, Zero, Sect and all the others were absorbed by Shin, warped Shin away from earth just as night fell, disappearing into the void of space.
As the No. 10 Angel Sandalphon, she has shown the ability to shrink the Giant Ophan to a tiny size, then revert it back to normal while making some design changes. This however, is not the true extent of her abilities according to Cross. She is not an O.P.T. but has shown herself to be adept at treasure hunting (due to her background) as well as solving riddles as shown in the ending chapters. Towards the end of the story, she was also seen using these shrinking powers by fighting one of the 4 Warriors of Zenom. In her battle, she was seen exhibiting enhanced strength and the ability to enlarge and shrink objects (such as rocks and etc) with ease. She also has extensive knowledge of ancient languages; whether this is dues to her being the host of Sandalphon is not very clear.