Kartatz, a middle-aged dwarf with medium-length hair, a thick beard, and a prominent mustache, serves as the youngest son and third child of Cayna. Entering public service via the Foster System, he diverges from his siblings through a demeanor defined by maturity, responsibility, and an unyielding sternness, cementing his role as the family’s most pragmatic member. Cayna’s open displays of maternal affection unsettle him, clashing with his self-image as a seasoned adult unaccustomed to such attention.

A skilled construction worker at Felskeilo’s riverside shipyard, Kartatz wields axes and hammers with equal proficiency in both labor and combat. Though he harbors deep respect for Cayna, he routinely discourages her from overtly doting on him in public. His interactions with siblings Skargo and Mai-Mai often cast him as a mediator, tempering their quirks with reasoned pragmatism. When Cayna once considered altering Skargo’s flamboyant nature, Kartatz defended his brother’s value to their nation and genuine devotion to their mother, prioritizing practicality over perfection.

Kartatz’s telepathic abilities remain an enigmatic facet of his character, their precise uses undocumented. Once regarded as Cayna’s favorite prior to her adoption of Luka, he retains an affectionate bond with her, addressing her informally as "御袋" (ofukuro)—a gruff yet endearing term for "Mum." His narrative presence anchors itself in unwavering reliability, emphasizing steadfastness over dramatic evolution.