Weeping of the Gods
Ten seasons ago, when the tribe lived near to the river, on a clear night a single huge orb of white light fell from the sky. As it fell the sky was brighter than the brightest sun, but pale and cold like moonlight.
When it struck the ground all the inhabitants of the savanna felt it inside them, but those who could work magic or speak to the gods felt it most. Their powers grew and the people rejoiced thinking this was a blessing as they became more able to communicate with their ancestors and work the land.
However, as time passed it became clear that this was a more complicated event. The dinosaurs, which had always lived in the savanna, now became more powerful and numerous, eventually forcing the tribe to move south, further from the river and out into the savanna.
The area the tribe was forced to abandon was named the Forbidden Zone.