The Paladins of Caelum Academy
There's an academy, in the kingdom of Arx, for paladins. Paladins are half-way between priests and knights, with some paladins leaning more towards the knightly side and some more towards the priestly side. They use a combination of Holy Spells and Sacred Weapons to defeat the demons of the void, and protect the world from evil. The students of Caelum Academy are training to become paladins, and are preparing for the seemingly inevitable war with the kingdom of Nihilus, a kingdom whose wizards openly practice demon conjuring.
------------------------------------------------
The religion of this setting is largely focused on stone imagery. The Law, the divine-written rules by which all people are meant to live, is written upon an enormous stone obelisk that supposedly rose out of the earth eons ago. Heaven is believed to be deep underground, protected by a layer of liquid stone (magma) that only good souls may pass through. Angels are believed to be beings made of crystal. Golems of stone are a common creation of paladins, and God can be spoken through via statues made of stone. Paladins' weapons are made of diamond. Basically, priests forge the weapons out of coal and then cast spells to turn the coal into diamonds. Demons are believed to come from the sky, particularly outer-space, and the sun is believed to be a mass of liquid stone that is meant to ward them off. Demons are creatures of "The Void," and are weak to weapons made of stone, especially diamonds.
-----------------------------------------------
Players would play as students and professors at the Academy, though later on we may need people to play the demon conjurers and villains. (Perhaps a second roleplay could be made for a demon-conjuring academy?)