Serena Rinnen holds high status in a Tower royal family, admired for her noble elegance. Before becoming a Regular, she raided merchant caravans to amass wealth, marking a shift from outlaw life to the Tower's challenges. Chosen by Headon, she ascends the Inner Tower as a Regular, distinct from Irregulars who enter uninvited.

In combat, Serena wields swords and melee weapons skillfully to shield allies, augmented by precise water-flow manipulation that unleashes devastating strikes and erects defensive walls. This fusion of martial prowess and elemental control heightens her battlefield impact.

Strategically astute, she aids in mission planning and tactical analysis, reacting decisively to crises. Her demeanor blends regal grace with steely resolve, particularly when confronting betrayal—such as challenging a Princess for abandoning tests and comrades.

She carries the rare ignition sword Narumada, one of seven sacred Hong family weapons. This blade channels shinsu energy into explosive blasts, though its full power exceeds her current mastery as an F-rank Regular. Serena's documented actions center on the Floor of Tests, notably during the Hide-and-Seek exam where opponents briefly seized Narumada. After clearing the 2nd Floor with fellow Regulars, she has not appeared in subsequent records.