The Sunstone Citadels

Also known as the Haunted Kingdoms or Northern Kingdoms, depending on who's talking. Any combination of these three names has probably been used at some point, but these three permutations are the most common (in order of mention).
Within this region, any patch of darkness can spawn aggressive shadow spirits, commonly known as haunts. This necessitates constant lighting of settlements for safety. Luckily, there's a somewhat common mineral known as sunstone which soaks up sunlight during the day and emits it at night.
A scattering of settlements found in the North. People tend to gravitate together by necessity due to the scarcity of sunstone, leading to very concentrated populations (generally at large sunstone deposits). The sunstone would be interspersed throughout settlements during construction in order to keep them constantly lit throughout the night.
The Sunstone Citadels have a long history of relying on Midlanders for important resources. They were famously thought of as at the mercy of Teria, given the extreme value placed on glass for construction and later on, Epacs' artificial sunstone.

Settlements

The kingdoms generally rely on a system of central settlements with high population densities sustained by nearby farming sattelite towns. Cities are generally built where deposits of sunstone originally stood, and tend to level out in size after these have been depleted.
Due to the dangers of poor building maintainence, even the lower classes live in very stable buildings. However, costs do have to be cut somewhere: fewer walls means fewer occlusions to light, so the first thing to go is generally privacy. There is a very strong culture of communal activities among the poorer classes.
There were once northern civilizations relying on lighting sources other than sunstone, though they collapsed rather catastrophically.

Military

Military forces in the North have the odd requirement of having two entirely different types of enemies to face: haunts, and each other. This results in every region having its own standing army due to the constant threats. Piercing weapons such as spears and arrows may be excellent at killing humans, but poor choices to face haunts with. Cutting weapons like axes and swords are far more easy to protect against both with armor and hard light (less energy to dissipate). Mages prove to be exceptional at combating both humans and haunts, but require extensive training and tend to have their own set of internal politics that may prevent them from killing opposing mages.
Typical troop distribution of a Northern city:
~500 infantry- axes/spears/swords and simple coats of plates. Technically peasant levies, but everybody is expected to have training due to the inherently dangerous nature of the environment.
~100 archers- note that archery isn't much of a survival skill since haunts make hunting a pain (and themselves are very resistant to arrows). The surviving wildlife is generally tough enough to kill haunts (other than rabbits).
~100 career soldiers- minor magical training (typically focused on shield generation) combined with better quality gear- tendency towards wearing mail.
~20-30 mages- various specializations possible, highly valuable as force multipliers.
~1-3 archmages- extremely powerful, but tend to be playing their own political games within the city's nobility, very rarely taking direct orders from commanders (often being the commanders themselves, given how they tend to be related to the ruling family).

Crafts

While the region is famous for poor ore deposits, a significant proportion of legendary smiths hailed from the area.

Conflict

It's important to note that once the sunstone deposits ran dry, there was a long stretch of time during which the only way one could expand was to raid another settlement to steal its sunstone. The fractured city's sunstone deposits are completely looted at the borders, for example.
Even smaller broken pieces of sunstone dust can be stored in distilled water for use.

Manufactured Items

• Glimmers