It's based on one of the historical theories of the spread of the Black Death! Where Mongol armies invading Europe would lob corpses into defending cities to spread disease and lower moral, and some of those corpses definitely were infected with the Bubonic Plague as that was just a danger of life on the steppe due to the eurasian marmot having it, but Europeans werenot ready. Its more likely it came from the increased stable trade routes especially with Genoan colonies in Crimea, but inspiration is inspiration.

this orbu'ur unit is very interesting

Outstanding work!