A war against magic.
The sentients feared these secrets and ostracized those who sought them. At first, these seekers of truth tried to convince the sentients that they were benevolent scholars only interested in bettering the world. But there were those that coveted the power that the secrets bestowed, and they began to use their knowledge for personal transcendence. This spurred even more fear from the sentients who, at first, merely banished these practitioners of ‘magic’ from civilization. But that only alleviated a nagging symptom, it did not cure the ill. The sentients could not allow a power to exist to which they could not control. And before long, the seekers were hunted down and destroyed, along with their secrets and their ‘dark arts’, plunging Athea into a state of ignorance and misguided superstition, a state of being that could be easily controlled.
A war against magic.