Roswaal J Mathers (ロズワール・J・メイザース), formerly known as Julia (ジュリア), was the grandmother of Roswaal L Mathers, the mother of Roswaal K Mathers, and the head of the Roswaal House two generations before Roswaal L Mathers.
Like previous generations, she had heterochronic eyes, with the left eye being yellow and the right eye being blue. Her long straight indigo hair was partially tucked behind her left ear and reached down past her shoulders. Roswaal's skin was as fair as porcelain and her bust was considerably large. Despite the fact that this iteration of Roswaal wore little makeup, her astounding beauty was still enough to captivate men.
Although her clothing was fairly different from previous and succeeding generations, she still stayed true to the general taste maintained by every Roswaal. Her ensemble, that was a uniform of sorts in deference to the Demi-Human War that was ongoing at the time, consisted of a pair of long black boots, white tights, a white long-sleeved shirt, and a purple jacket with golden lining and rolled cuffs that was worn over the shirt, essentially obscuring the white garment from view. Her cleavage was not covered by the shirt nor the jacket, essentially meaning that it was exposed. Like her grandson, Roswaal wore a long black cloak that nearly trailed along the ground and had a red interior
Julia sacrificed herself to save Carol Remendis, dying in the process, even though she hadn't expected to die at that point in time because it was not written in her Gospel. Galic Fabless' son was born, not from love and marriage, but because Julia simply wanted his offspring in order to retain someone of his talents and birth a child who'd be apt in healing magic.
Master Martial Artist: In order to counter the powerful magical abilities of Sphinx, Roswaal cultivated the body of Roswaal J. Mathers to be a master martial artist rather than a master mage. From a young age, Roswaal painstakingly trained her body in the martial arts. Over twenty years, her training coupled with her natural talent forged her into a true fighting genius. Anyone who saw her in combat could tell that she was an accomplished practitioner with a flawless technique. Her style was based around landing lightning quick and precise punches that sowed ruin upon the bodies of her enemies. Although his later bodies like Roswaal L. Mathers probably weren't as physically powerful as Roswaal J. Mathers, they still maintained the fighting techniques Roswaal had coalesced during that particular life, meaning Roswaal remained a true master of the martial arts.
Superhuman Strength: The physical strength of Roswaal J. Mathers vastly surpassed that which was accepted as possible for a human being. Her mighty blows were powerful enough to snap bones, rupture internal organs, shatter boulders, and split large trees in half. She could throw small-yet-heavy steel balls with enough force to shatter bones and organs.
Yellow Eye: Roswaal is able to use his yellow eye to break magic apart. This was first seen when Roswaal J Mathers fought against Sphinx and destroyed her Magic Circles with her Yellow Eye.
- Book of Wisdom (叡智の書): Just like Beatrice, Roswaal was given one of the two complete copies of the Book of Wisdom Echidna created before her ultimate demise. It allows Roswaal to use a limited version of the original Book of Wisdom, as it shows her a detailed path to her desired future. For four centuries, Roswaal strictly acted upon the Book's writ, doing exactly as it was written.
- Metal Throwing Balls: A type of projectile Julia specifically used for fighting Sphinx. Despite their small size they contained a lot of mass that allowed them to penetrate deep into the target's body, dealing significant damage.
- Roswaal's Black Gloves (ロズワールの黒手袋): Roswaal J Mathers possessed two black metal gloves which she used during combat. It's said those gloves were given to her by one of her ancestors, and were even capable of stopping the edge of the Sword Saint's blade.
- Starting with his original body, Roswaal has been changing his middle initial every time he possesses a new descendant. His original initial was A, making his current body his 10th one.