Canon Mythos - The Wolf at the End of the World
A thousand years ago Maka, the spirit of the land, roused herself and her fellow spirits and violently revolted against the pollution of the world, killing millions.
A core (and relatively new) part of the Maenar religion is the idea that the Earth spirit will return and consume the world if not given its due respect. In order to appease it it is a Maenar tradition to bury the dead and return them to the Earth. Valeyrians, on the other hand, are far more adversarial: believing that the spirits are dead and unable to reach them, they burn their dead in defiance.
The murderous debacle a millenia ago is what spurred Manarfell into pursuing alternative energy and ultimately resulted in their bio-sustained public lighting system.
The Blight have a similar story, though theirs is focused on the destruction of their relic, the Restless Heart.