Rush Valley & Xerxes Arc

Ed learns automail crafting while discovering the ancient civilization of Xerxes and the origin of the Homunculi.

The Rush Valley and Xerxes Arc occupies a transitional space in Fullmetal Alchemist — the series pausing after the trauma of Laboratory 5 to breathe, widen the world, and plant the seeds of revelations that will reshape everything. The brothers travel to Rush Valley, the automail capital of Amestris, where the mechanical engineering craft that defines Ed's prosthetics is elevated to an art form. Their stay there — which includes Ed helping deliver a baby in circumstances that are both comedic and humanizing — provides a character-focused interlude that demonstrates Arakawa's mastery of tonal range. But the arc's greater significance lies in its geographic and mythological expansion: the ruins of Xerxes, the ancient civilization destroyed in a single night, begin to appear in the brothers' research. Through Hohenheim's history — their absent father, a man who seems to carry centuries on his face — and scattered archaeological evidence, the brothers begin assembling the outline of a conspiracy that predates the Amestrian state by centuries. The introduction of Ling Yao, the Xingese prince who has traveled from an Eastern empire to seek immortality for his own political ambitions, adds a new cultural perspective that will become crucial to the story's development. Ling brings with him bodyguards who can sense Homunculi through their disturbed aura, a skill that gives the heroes a tactical advantage they desperately need. The arc ends with the Elrics' understanding that the Philosopher's Stone, the Homunculi, and their own father's long absence from their lives are all connected to a plan of incomprehensible scale.