This is my first entry in one of these contests, and I'm doing it on a vastly outdated form of paint with no features at all to speak of. So I apologize for its low quality in comparison to others here.
The set up of this map is an eruption of the Yellow Stone super volcano (though downgraded in areas to keep human civilization alfoat) [Or if necessary a preexisting Volcanic Eruption in the Americas made considerably worse]. Originally it was set up to be 50 years after the eruption, or even less. However, I decided to lengthen it to allow for a full show of possible migrations. Roman Rule, as expected, virtually collapses. Climactic change and a few years with summers so timid that most starved. The Romans weren't the only ones with problems as various slavic and germanic tribes entered Rome in search of, primarily, food. Much of Europe had become baren, and Roman military power waned into nothing. The Roman Empire panicked and Rome was ransacked by the Romans long before any of the foreign tribes moved in.
The Visigoths, the Burgundians, the Franks, and the Magyars were amongst the largest groups that moved in. The Visigoth invasion was not fatal to Roman Rule, settling in the center of Iberia they actually provided a small bulwark against the remainder of the Southern Roman State. Other groups advanced beyond the Pyrenees, but most were defeated by the groups that followed them.
Two decades after the eruption things began to settle. Farm land once again started growing food enough to sustain the Empire, an Empire that had all but surrendered most of its bread basket in order to secure a few minor plots of land that could either grow food and fish the seas (seas which were now starting to be dangerously low on fish). North Africa was amongst the most prosperous of growing lands and the Empire shifted much of its focus there. The population of towns and cities there were more than three times that number in Spain, and five times that in Italy. Rome, itself, became a mere shadow of its former self. Capital in name only, much of the government was carried out in Tunis. Even though this slight normalization had led to the resurgence of Rome, it was still weak. Unable to project its power, and even unable to truly defend itself, it used its influence and wealth to forge ties with some tribes in order to provide protection from other invaders and in return received food and other goods. The most important of these groups would be the Magyars, which had settled in the Po-River valley.
Recently Rome has begun to reclaim its former Empire, the coastline of Dalmatia were captured by the the 23rd Roman Emperor to take control since the eruption. The Eastern half of Rome fared much better. By way of the east, actual glaciers began to form, blocking most incursions and terrifying others, while the way by west had been looted by the Romans themselves and the rocky lands of the Balkans were far less inviting than Roman Gaul, Dalmatia, Iberia, or Italia. Colder as well. This did not prevent rapid collapse of Roman control, it simply managed it better. Much of the Balkans were quickly abandoned without a second thought. The Vandals attempted to set up shop there after the Romans left, but unable to properly feed themselves they collapsed into ruin.
In the decades that followed, however, a massive wave of people from the Russian Steppes advanced south. Related to the Cumans and the Turks, they used cavalry as a primary tool to capture resources. As they advanced both the Romans and the Persians had little to stop them. Gradually they came down to the point where they feasted off of newly grown supplies, barely settling down in the lands between Rome and Persia. That, and, they were starting to become countered by standing armies. Feeble ones, but still imposing when the invaders never had to fight actual battles to pillage the starving before.
A similar invasion occurred from the Turkic people of the steppe on the eastern side of Persia. Already powerful rivals to the Sassanids, driven to madness by starvation they attacked further and further south. A struggling Persian state regressed inward and southward. Saved only by the mountainous terrain, now frigid by falling temperatures, which created a shell protecting the Persian heartland from the outside world. The Persian Gulf became the lifeblood of the Sassanids, who jealously guarded it.
Elsewhere civilization regressed. During this dark age a number of Christians proclaimed that the unveiling of the end of the world was to come, and a number of people claiming to be Jesus Christ appeared throughout the era. The massive influx of pagan foreigners also created a chaotic religious scene. By the end of the century, however, Christianity had won out in the West, while in the East it was proving to be a more than even match of wills. Most people who are not near, or around, the few centers of civilization are either dead or incredibly lucky hunter-gatherers. All the various peoples of Northern Europe and Asia flooded south. Once distinct groups became inseparable from others as the dash in search of food had mixed the groups by concentrating them so much so that they no longer functioned independently anymore. What was left of the Saxons, Angles, Jutes, and others suffered this fate. A thin veneer of human civilization crops beyond the borders of the established states. These, while civilized and having some organization, are not states to speak of. They merely represent villages and towns that exist largely separate from any sort of authority surviving off of trade and subsistence.
In the year 517 A.D. the future was gradually beginning to become bright as human civilization survived its greatest test since they have developed civilization.
