Forenote: the Human Realm isn't in modern times. Their technology includes medieval weapons and spooks' tools. They live in somewhat medieval alternate Earth
The Dark had claimed the Equestrian Realm, and a few more scattered through the stars, and so had The Light. But there was one realm that The Dark was trying desperately to claim. The was known by most as the Human Realm. The Dark's box had not been found in that realm, but the power of his worshipers gave him opportunities to briefly use his power and even appear on certain days. He wanted this Realm.
The Human Realm had people that worshiped The Light, known as god, and those who worshiped The Dark, known to them as The Fiend. They were gods to the people. Those who fought to serve The Dark were known as his servants. There are many different servants to The Dark and they worship him in different ways.
Most people directly worshiped neither, and those would be sent to Limbo. The worshipers of The Light had two kinds of people that worshiped it directly. Those were priests and those who feared a bad afterlife.
There was one profession that were warriors that fought for The Light, without worshiping it, just believing. They were known as spooks. They were similar to knights for a king, but they didn't fight to get into heaven, but to defeat The Dark forever. They usually fought The Dark and it's servants without direct weapons, but they fought with knowledge.
In the human world, spooks are very uncommon, but incredibly necessary. The amount of dark servants had been steadily increasing, and The Dark was creeping up in power, close to being able to being summoned into the Human Realm, to fully take over.
The Human Realm contains people known as scryers, who can supposedly see into the future. There is a widely known prophecy that some believe. That prophecy states that John Gregory, a spook, would have an apprentice named Tom Ward. Tom Ward is said to become the most powerful warrior in the world, able to defeat The Dark itself in the Human Realm...or to be able to banish The Light from the Human Realm. His fate is unknown even to him, as he fights for The Light, but has darkness inside of him.