My current dungeon has a very schematic Environment:
Umbral Concentration Tier Ⅱ.
Terrain difficulty 10 - the complex was professionally engineered, and those original engineers are still maintaining it in their unlife.
Magic difficulty 18
Restless Dead: the dead rise automatically as "fresh zombie," and all embodied undead rise immediately on a 6 on 1d6. Newly dead take about 5 minutes to rise, unless rituals to give a permanent repose are used.
Shades, too: Each person dying has a chance of becoming a specter of themselves. Throw 1d6, on a 6, a spectre arrises, too. Use the best fit Spectre template.
Firmly Umbral: The magic difficulty is for spells affecting the environment; spells affecting adversaries or allies are unaffected.
Openly Magical: anyone can do minor magic effects, up to dismissing an incorporeal or semi-corporeal undead, by appropriate narration and a suitable difficulty 18 roll.
Troublesome presences: When resting, the GM rolls 2d12 on the umbral table and discards the higher. If there is a watch set, the roll is 3d12, keeping the middle die. Use the standard rest effect table.
Fresh Zombie: use the skeleton warror or skeleton archer templates but lack the "only bones" feature.
Now that I write it out, it's a bit stiff...
But that 18, well, the wizard has hit it for preventing the Ribbet raiders from rising. Several times. He's a Fungril, and is binding his spores into them to make them rise next month as new Fungril. His lore addition...
Our Warrior, Sir Vynčent, confronted with a Spectral Captain, the shade of a dwarven knight who died as the umbra descended, and was ordered to "hold until relieved," stepped up, said, "I relieve you, Sir."... and hit the difficulty... so, the spectre was able to discorporate and seek his afterlife...