Thousands of years ago, the primitive tribes used to sacrifice people by drowning them in the nearby moor. When civilisation reached the land, the moor was dried up, and a road built across it. But then the kingdom fell into disarray and this remote part of land was abandoned to the rustic locals and civilisation withdrew its light. There are even whispered rummors that the sacrifices have begun again. Be as it may, whoever tries to travel the northern road will discover that the marshland has reclaimed it again. Will you dare the moor and find the other end? But beware, there is some new force at work here, and the dead seem to have trouble finding rest.
Area 1: The marsh
The marsh is a large area of sparse vegetation full of wispy mists and the stench of rotting wood. The road disappears beneath a good feet or two of dirty water, and it soon becomes untrackable. Traversing the march counts as very difficult terrain.
The only noticeable landmark are the hills to the North, some dozen miles away.
Underwater, the victims of the ancient sacrifices stir. If they sense a character nearby, they will rise out of the water and try to drag their victim underwater. A bog-zombie can only survive outside the water for 1d8 rounds, and will dive again after that, trying to fill its mouth with the mud from the marsh floorbed. The closer to the hills the characters get, the more frequent these encounters will become (0 in 6 chance on one end, +1 for every two miles traversed).
If the characters are out at night, they might see large, arm-sized bugs droning around in the air, seemingly coming and going to the north. The bugs are scavengers and feed on carrion, and will attack and try to eat the bog-zombies if they encounter them.
Area 2: The witch's hut
If traversing the march, the characters have a 3 in 6 chance of finding the old witch's hut, 5 in 6 if they explore the marsh meticulously. The hut is built above the water, standing upon several wooden poles. It can be accesses by climbing a rope ladder.
Inside the hut itself is just a small stove, a smelly bed with a nest of blankets, a table with some knives and kitchen utensils and several shelves with jars, pots and pans, containing some rabbit meat, herbs and vegetables.
The witch is at home for most of the day, and goes hunting or gathering food in the mornings (in which case she will avoid the characters and will be impossible to track, she knows the marsh too well). If encountered, she will not be hostile (unless threatened), but will not be friendly either. In her house, the witch has about a half dozen sacrificial victim heads hung up on the wall. If questioned, she will tell that she killed the zombies herself and brought them home to question them about the secrets of death. If pressed about it, she will fetch a jar of mud, and stuff a fistfull into a head's mouth, making the head come alive, but it doesn't seem to be capable of coherent thought or speech, groaning and snapping its teeth. She will explain that the mud makes the dead come alive. She does not know how or why, but the undead seem to be more common closer to the hills.
Area 3: The caves in the hills
If the characters reach the hillside, they will see the other end of the road emerging from the swamp and continuing to the north. Near by the road is a cave entrance, with a spring emerging from the darkness and feeding the swamp. Around the cave entrance, the bog-zombies will rise from the water without fail.
If approached at night, the large bugs can be seen entering and leaving the caves.
If the characters decide to investigate the caves, they will find a complex underground network of partially submerged caves that can be navigated by following the water upstream or downstream. The water here seems to be warmer than outside.
There are no bog-zombies in the caves, since no victims were ever sacrificed inside. The undead plage is recent and has nothing to do with the actual sacrifices.
Area 3.1: The mushroom island of the carrion bugs
When traveling to and from the spring, the characters have a 2 in 6 chance of happening upon a cavern with a small island rising out of the water. There is a groove of very large, faintly glowing mushrooms growing on the island. The mushrooms are about twice the size of a man. In the center of the groove is a nest of the bugs. If disturbed, the bugs will defend their home and attack ferociously, even if they seemed harmless before.
Area 3.2: The muddy spring
If the characters try to follow the water flow to its source they will eventually arive in a cave where the water is bubbling out of the ground, it carries with it a deep black, thick mud, like the one that the witch stored in her jar or could have been observed being eaten by the zombies after their short period above the surface. If inspected with magic, the spring appears to be magical. A person very knowledgeable in the arcane might discern that there appears to be some sort of a planar rift just below the surface where the water emerges. Indeed, if probed, there is just a hard rock floor beneath, with no openings.
The arcane knowledge will also suggest that the rift can be closed (perhaps only temporarily) with a ritual sacrifice of a live being. If the characters decide to close the rift, the water will subside. The bog zombies will remain active but will cease to rise from the dead after a fortnight.
#Appearing 1d3 per each encounter, +1 per each 2 miles closer to the cave entrance
Attacks: 2 hand+0 (1d4)
Special: Half damage from slashing weapons.
Can grapple automatically if it hits with both arms.
#Appearing 1d4 outside, 2d8 in nest
Attacks: bite +2 (1d4)
Special: Carrion breath, +2 fortitude attack to apply the nauseated condition
Attacks: cold hands +0 (1d8 damage)
Curse, +4 will attack to apply the shaken condition
Ancient Black Fury, +2 to constitution and strength
Flight 60 ft.
*Some of the bog-zombies carry ancient jewelery of bronze (1 in 6 zombies) that's worth 1d4 copper each to the right people.
*Inside the nest of the carrion bugs there are a few human and animal skeletons, one of which still has a pouch with 17gp inside.
*If ransacked, the old witch's hut contains nothing but worthless, old and dirty cuttlery, tools, bones and clothes and several days' worth of food.
*If the characters travel along the submerged road, they have a 3 in 6 chance of happening upon a wrecked, half-submerged merchant wagon. Most of its wares are useless and destroyed, but there is a coffer containing a trading bar worth 50gp and a dirty old rapier wrapped in leather skins which can be restored to a masterwork quality if cleaned and honed.