Players' Classes were determined by some innate sense within the Player. The most common time of determining was around three years. Each class worshiped a deity. Since the fall of the Ovarch, the Creators had faded from the memory of the Players. A myriad of gods eventually came to be known among the Players, each vastly different than the others. These gods were not like Creators. They drew their power from the legions of worshipers before them, not from the whisperings of the Universe.
The Creators were forgotten for ages until a Player named MatPat found inscriptions upon walls of Abandoned Mineshafts left behind by the Miners of the Ovarch. He realized that there had been a civilization long before the current society of the modern Players and began a search for the true meaning of the world. His findings became known as The Theory. It was both dismissed and accepted by many until Librarians found ancient texts dating back to the very earliest days of the Ovarch and before. One such text was the journal of Steve himself. It contained forgotten methods of building, mining, and crafting. It also held the story of the battle between he, Alex, and the Wither. Stories about Notch, Herobrine, Ender, and C418, long considered to have been folklore or myth were now confirmed to be true. But all that knowledge came at a price.
While the Creators drew much of their power from the universe, they also relied upon the Players and Villagers to remember them, much like the gods Players worshiped. With the sudden influx of knowledge about the Creators, Notch, Ender, and C418 were able to appear in the world and walk among the mortals. And Herobrine was one of the Creators. He gathered enough power to begin appearing in the world before Players and was even able to interact in very weak ways with the world, carving tunnels into mountains, building pyramids deep underwater, and shearing leaves off trees. Through these actions, fear spread among the Players and they began whispering of Herobrine the Demon. Such fear gave him power and his power grew. When it was revealed that Null and Entity were his lieutenants, they too began drawing power from the masses. Soon, the third coming of Herobrine would be nigh. And there was nothing that could stop it.
I'm probably gonna add more stuff as I go, making this into an encyclopedia of sorts. If you want something added PM or drop a review and I'll do my best. Later! -RFA