Short answers, pulled from the story.
The post-classical history period stretches from roughly 500 CE to 1500 CE and is defined by the expansion of civilizations into new geographic areas, the rise of three major universal religions, and the development of vast trade networks connecting distant lands.
A volcanic eruption in El Salvador in the year 536 sent a cloud of sulfur into the atmosphere that plunged the entire Northern Hemisphere into darkness for over a year, causing crop failures and mass migrations that would reshape the fate of empires.
The post-classical history period saw the rise of Islam between 610 and 632, the spread of Buddhism from India to China, Japan, Korea, and Vietnam, and the establishment of Christianity as the state church of the Roman Empire before spreading into northern and eastern Europe.
The Mongol Empire created a safe environment for travelers like Marco Polo and Ibn Battuta to journey across Eurasia, facilitating the exchange of goods and the spread of the Black Death which killed between 25% and 50% of populations in Eurasia between 1347 and 1351.
Native African Islamic empires including Ghana, Mali, and Songhai rose during the post-classical history period, with Mansa Musa of Mali being the wealthiest person of his time in the 14th century and African civilizations becoming essential sources of gold for Christian Europe and the Islamic world from 1100 onward.
East Asia during the post-classical history period saw the spread of Confucianism and Buddhism, the development of centralized governance, and innovations such as gunpowder, woodblock printing, and the magnetic compass that spread to the Islamic world and eventually to Europe.