On the first day sentient creatures were granted a soul, and with it came clarity and understanding.
On the second day, a soul consuming demon was planted and with it came corruption and madness.

The northern kingdom of Equestria, an economic powerhouse and leader of technological and military innovation via implementation of soul-channeling has succumbed to the demons. Isolated by an expanding deep colourless fog, many entered, none escaped. Until Scootaloo one of the two royal fangs escaped, and told the world of Equestrias plight. How demons stole souls adding to their power and driving victims mad, attacking those with souls. Enticed by the power of mature demon souls more people entered Equestria but still none returned. One hope remains Gilda a prisoner thrown into the fog for unknown crimes.
Set after The Crystal empire two parter but before Twilights ascension.
Crossover with Demon souls and MLP both of which I do not own.