The deposition of the last Western Roman emperor in 476 is traditionally taken as the end of the Western Empire. The date is a marker of convention, not a sudden break: the collapse was a process spread over centuries. The empire had already been administratively divided, and its eastern half (later Byzantium) continued for another thousand years.

The causes are not single, and historians debate their weight: prolonged fiscal and military strain, internal instability, the pressure and settlement of frontier peoples, epidemics, and climate fluctuations. Whether it was a "fall" or a "transformation" is also debated; many institutions, the language, and legal traditions continued within the new kingdoms.

The consequences were structural: centralized taxation and the standing army, the scale of long-distance trade, and urban density declined in the West, and political authority fragmented. The local power centers, church institutions, and migrating peoples that emerged in this gap laid the foundation of the later medieval European order. This is also where Eon's period scale shifts: from the century-scale of antiquity to the Middle Ages.