From the introduction:
At some time, a series of plagues passed over Jorth. Different societies have different tales of this time, but the most common include: famine, pox, leprosy, magical war, wrath of the gods, monstrous invasion, fire, flood, and freak weather. After many years of being subject to these repeated plagues, Humankind, and their brothers, Elves, Dwarves, Halflings, etc. were able to rise again and begin their return to greatness.