Joi

Joi is practical and professionally focused. Her limited appearances emphasize competence and familiarity with the unusual medical problems created by life at Briggs rather than a detailed personal storyline.

She treats automail as both machinery and a medical concern. In the northern climate, understanding how metal prosthetics affect circulation, tissue and body temperature is essential to keeping soldiers operational.

Joi has no established alchemical abilities. Her expertise lies in medicine and automail engineering, particularly the physiological effects of extreme cold.

She understands why standard steel-heavy automail is poorly suited to Briggs and works with cold-climate prosthetics designed from lighter materials with reduced thermal conductivity.

Her medical knowledge makes her part of the infrastructure that allows Briggs soldiers with prosthetic limbs to function in conditions that could otherwise cause severe cold injuries.

Joi appears as part of Fort Briggs's medical and technical staff during the Elric brothers' stay in the north. Her work helps explain the specialized automail used by soldiers stationed there.

Her role is primarily world-building and logistical. The Briggs arc emphasizes that survival in the north depends not only on elite soldiers but also on engineers and physicians capable of adapting equipment to extreme conditions.

Buccaneer uses specialized combat automail suited to Fort Briggs, placing his continued maintenance within the sphere of the fortress's automail specialists.

Neil is another automail engineer associated with Briggs and its specialized prosthetic technology.

Edward Elric experiences firsthand why his ordinary automail is poorly suited to the extreme northern cold after arriving at Briggs.