The Telluric Threnody
Humanity was, long ago, measured and categorized by culture or city state. Different subraces could be distinguished and were driven by isolation by geography or religion. This changed dramatically due to The First Tearing.
Now humanity is isolated and huddles around powerful figures, at once needing their protection and chafing at their rule. Ten generations since The First Tearing noticeable effects can be seen on the human descendants of those who live near the planar rifts. People begin to show subtle to outright obvious signs of Planar Corruption.