Setting the Scene
You start in a small walled city (really, a small town by our modern standards) called Littleview, at the edge of a tall cliff, above a deep and wide valley. The town has a ring of fields around it, and then empty scrub, and finally the edge of the forest. Littleview is a cosmopolitan town, populated by a mix of races, though dominated by hill dwarves and humans. The local economy is dominated by trade, for Littleview sits above a steep Path down the cliff, which leads to dwarven halls accessed through the cliff face. It is the only local source of fine metal goods, and Littleview is literally built on the start of the Path, so controls access and charges hefty tolls for access.
Two other, heavily used and maintained, Paths run along the top of the valley wall, one each way, which lead to local communities, and fan out further. This makes Littleview if not a heavily traveled hub, at least more heavily visited than any of its immediate neighbors. Strangers come through often and trade, or pay the toll to climb down the Dwarven Path.
The shallow parts of the forest are used for hunting, lumber, and firewood enough that they are not really wilderness, but things wander in from the wilderness often enough that most folk choose to sleep inside the city walls at night. The King, Rahm Littleview, maintains careful order and regular patrols into the forest to ensure nothing too horrible festers and that the dead are kept at rest.
Recently, intermittent bands of refugees have come through Littleview, down the Path from Millhouse along the valley wall, to the north. Some are sponsored for citizenship, if they have particularly needed skills, but most are encouraged to keep going, as the small farms around Littleview are not particularly fertile, and it is dangerous to expand them into the scrub. They continue south, towards Kingdom of Fallwash, a collection of several cities under united rule, where the valley opens into moorland down the southern Path. They carry tales of horrible battles, with too few left afterwards to burn the dead, leaving destruction and chaos in their wake after. But they say they have traveled a long way, a dozen or more Paths to arrive here, and the troubles are far away in places the folk of Littleview have barely heard of.
On a clear day, those with good eyes can see the roofline of a city on the far edge of the valley, many miles away. Sometimes, at night, there are sparks of light there as well – bonfires maybe? No one has ever figured out how to get there, as far as anyone knows! Travelers native to Littleview often take drawings of the roofline when setting out, in case they ever reach a city which matches it. What fame would come from answering questions about this place!
Okay, the intro makes some assumptions, here is an infodump to make sense of them.
These are not in any way meant to limit you, but to give you some ideas of directions we could go, at least to start with!
Some images to capture visual moods for the environs:
Generally a bureaucracy in most settlements, though the details vary wide. Commonly has several aspects, often called Orders. The orders of the temple will often have a local name in a region, but are collectively referred to as "the temple". This often annoys the politically minded members of various Orders as they are not usually associated with each other in any formal manner. That said, they often cooperate, given that they tend to focus on the proper functioning of society in a strange world, just of different aspects.
Deals with funeral rites, avoiding creating undead, and dealing with undead that arise. Most folks are generally intimidated by these folks as they have their death association, but also because they are one of the classically armed orders of the Temple -- after all, they deal with undead problems. Clerics are usually of the Grave Domain, but can be of others.
Imagine the folk from Katherine Addison's works who deal with the dead, minus the criminal investigation angle. Or, imagine the Order of the Bastard from Bujold -- except every untimely death has a good chance of spawning a demon.
Seeks to understand how and why the world works as it does, particularly where it seems that causality breaks down. Fundamentally cosmographers. There is a distinct division in the Order of Mysteries between those who theorize on why things work the way they do, and those who gather data (referred to as "givens") in the world about them. The theoretical side are referred to as Theoreticians or Theors, the agents who gather givens as Investigators.
Imagine the mathic folk Stephenson’s Anathem, except without the Consents, and add in the romantic version of Victorian explorers, or Indiana Jones crossed with the X-Files, for the Investigators who gather givens for the Theors. A given Investigator is generally associated with a particular Theor or group of Theors, and investigates phenomena of interest to them.