A young treasure hunting girl who is researching the mysterious, legendary O-Part. She carries an extensive knowledge of ancient languages, and her other objective is to uncover the mystery of her father Jack Crescent's death. She carries a necklace (Jade Pendant) her father gave her, which is revealed to be a S Rank O-Part with over 100 effects. She is 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 friendship bond with the two, but seems to have more intimate feelings for Jio, and she has known him much longer. She is later revealed to be Sandalphon the No. 10 Angel and her "father" is actually a traitor to the Stea government and is not really her father, just a man who was taking care of her until she awakened as the No. 10 angel, though she still considers him as her surrogate father. Her soul is absorbed into Jio in the Olympia chapters when Satan is fighting Cross and gets a fatal wound. Post-timeskip Jio and his friends fight their way into Stea main base and Jio is able to reverse the absorption effect and restore Ruby's soul to her body. She is now able to use her Angel powers, though they aren't complete as of the latest chapters. After Ruby is reunited with her father, the leader of Zenom, 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 and inserted into the Kaballah. Inside shin to save the world with the help of Jio, Cross, Zero and Jack himself they warped shin away from earth just as night fell disappearing into the void of space.
As the No. 10 Angel Sandalphon, she has currently 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 however, 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 latest chapters. In a recent chapter, 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.