Iseria Frost serves in the Northern Jaegers, Zemuria's largest mercenary corps. She has deep blue eyes and short blonde hair. Her standard attire is a variant of the Northern Jaegers uniform: blue armor plates over dark green combat trousers with utility pouches. For reconnaissance, she switches to a disguise comprising a red dress with golden tassels and a white combat jacket featuring puffed sleeves.

She specializes in orbal guns and is a highly skilled sniper, making her a formidable asset within her platoon, which includes Martin S. Robinson, Lavian Winslet, and Talion Drake. The platoon undertakes high-risk missions, such as a covert operation within the Erebonian Empire to gather intelligence on perceived threats to North Ambria.

Iseria maintains a light-hearted, often carefree demeanor atypical for a jaeger, believing activities should be enjoyable to avoid wastefulness. This outward personality masks her underlying operational competence and strategic acumen. Despite her casual approach, she harbors deep concern for her homeland, North Ambria, which suffers severe economic hardship following the Salt Pale disaster.

Her character evolves during the Erebonian mission. Exposure to the Empire's comparatively peaceful and prosperous society prompts internal reflection. While helping Lavian Winslet reignite a commercial hot spring, Iseria confronts the stark contrast between life in the Empire and the harsh, militarized existence in North Ambria. This leads her to question the role of jaegers in a peaceful world and contemplate her place within North Ambria's society.

During the Northern War conflict between the Erebonian Empire and North Ambria, Iseria participates in defensive efforts. She collaborates with both Northern Jaegers and imperial Soldats against common threats to protect civilians, demonstrating her commitment to safeguarding lives regardless of the political conflict. Her loyalty to North Ambria remains consistent, but her experiences broaden her perspective on peace and conflict.