Jörmungandr belongs to the dragon clan of the fantasy realm Aquafall. Adopted alongside her three younger sisters by a team of miners who became her adoptive fathers, this family unit defines her core background. She feels deep affection and fervent loyalty towards her fathers and sisters, actively participating in household duties and assisting with deliveries like transporting coal, demonstrating her commitment to supporting them.

She possesses notable superhuman strength, enabling her to lift massive boulders and effortlessly heft a giant axe in her human form, likely enhanced by magic rather than inherent elemental power. This axe is her primary weapon, carried regularly and used in combat. Transforming into her earth-affinity dragon form grants her serpentine features and horns but no wings, further amplifying her physical capabilities.

Jörmungandr exhibits a straightforward, tomboyish personality with a simple lifestyle. She frequently acts on impulse without overthinking, as shown when she endangered Bahamut by throwing her axe to rescue her from a swamp. Her thoughts often center on basic needs, like a pronounced craving for beef bowls, which can distract her at critical moments. She also struggles with occasional forgetfulness, such as recalling names like Bahamut's or Syrup's.

Her development centers on a growing dedication to defense. After a mine collapse trapped her fathers, she exhausted herself digging to reach them, showcasing fierce protectiveness. This event and subsequent battles against Toripu creatures solidified her commitment to the Aquafall Defense team. She formally joined to extend her protective role beyond her family, driven by a desire to be helpful. Relationships with fellow dragon girls Leviathan and Bahamut evolved from camaraderie during a tavern brawl into a dependable fighting trio, though she occasionally clashes with Bahamut over differing priorities.