Marshwalkers
A marshwalker is a large semi-humanoid creature that appears to be made entirely of plant material. Within the Empire they are primarily found in Bregasland, Kallavesa and Therunin, but they may appear almost anywhere that the marshy conditions they favour can be found. They are also found in the lands of the Druj, and the barbarians sometimes bring them along on battles. They are perhaps most dangerous when exposed to the essence of a vallorn-corrupted environment.
The creatures themselves are not common, and generally not a threat to humans who give them a wide berth. Unfortunately, their migrations often take them near human settlements - and the beasts show little inclination to detour around them. Attempts to divert a marshwalker exodus are complicated by their resilience, their resistance to fire (they are simply too damp to burn), and their ability to smash through most obstacles placed in front of them.
One problem with marshwalkers is that, in their natural state, they are simply a colony of little slimy blobs that are virtually indistinguishable from the mud in which they live. In this state they are no threat to anyone, being primarily concerned with eating small insects, fish and plants and splitting into more tiny, nonthreatening blobs. It is only when they feel threatened, when some biological urge inside them decides it is time to move, or when someone starts building a structure near or threatening their habitat that the colony comes together to assume the much more dangerous form of a wood-armoured humanoid.
Appearance
Marshwalkers appear to be masses of vegetation coated and held together with thick slime. They are often encased in wood and stone fragments that appear from a distance to be nothing less than armour. The beasts seem to intentionally seek out this coverage in the same way that certain crabs seek the shelter of empty shells.
Studies by Marcher and Navarr naturalists have discovered that the marshwalker itself is actually a colony of innumerable tiny creatures similar to slime mold. A marshwalker is created when an entire colony comes together to travel to another location - either due to some migratory urge or to avoid some threat to their habitat.
Marshwalker capabilities
Marshwalkers are preternaturally tough. They can take punishing amounts of damage and continue moving; as long as they have access to fresh vegetation and water they can heal almost completely within a few hours from anything short of total destruction. Their powerful vitality coupled with their lack of vital organs and thick armour means it is dangerous to assume that just because a marshwalker has stopped moving, it has been defeated - their unstoppable advance is often merely slowed by weapon attacks.
Marshwalkers are 'large. Like all such creatures, they are unaffected by many spells and martial tactics (OOC note: they do not suffer the effects of combat or magical calls, although they still take damage from any blows struck to deliver them.) For example, they cannot be poisoned by conventional blade venoms nor knocked down with a pole-arm strike, and while arrows can wear down their reserves and cause them to retreat they do not have the devastating effectiveness they demonstrate against man-sized enemies.
Marshwalkers are mighty. Even a heavily armoured apponent can be bowled over by one of their sweeping blows, and they can shatter a shield or pole-weapon to flinders if it gets too close. Some rare marshwalkers have been encountered that secrete poisonous slime that weakens or even occasionally paralyses opponents. In a very few rare cases, marshwalkers who have been exposed to the vallorn carry with them the miasmic taint of that corrupt environment, envenoming everyone who comes nearby.
Finally, Marshwalkers appear to be inimical to manmade structures. They can tear down minor fortifications in a matter of a few hours. They quickly smash through barricades and other hastily-erected structures designed to try and divert their migrations, and when they move through a human settlement they tend to leave damaged and collapsed buildings in their wake. There are incidents where the Druj have used groups of them to assault gates or towers; while the destruction they wreak is by no means instantaneous, it is thorough and almost irresistible.
Culture and Customs
Marshwalkers do not possess a culture. They are clearly aware of their environment, but they appear unintelligent as humans understand it. They can be cunning, and they are capable of spotting and responding to changes in their surroundings, but they do not have a language, do not speak, and appear to respond to tone of voice only. They are known to issue great echoing horn-like moans that travel great distances across the marshes - there are some reports of colonies assuming humanoid form apparently for this sole purpose. Naturalists have suggested that these serve a similar purpose to wolf howls - communicating over distance simple messages between colonies.
Primarily they are motivated by their desire to move from one place to another; to protect themselves from threats; and to smash man-made structures they come across. Left to their own devices, they generally collapse back into their component parts once they reach their destination or once the immediate threat (or man-made structure) is removed.
Colonies are aware of each other and appear capable of rudimentary co-operation, although they generally fight as individuals. While they often move in a loose group, a band of marshwalkers make little attempt to come to one-another's aid during a fight.
The Druj appear to control small groups of Marshwalkers through the use of Spring ritual magic; the specifics of this magic are unclear to Imperial scholars. Marshwalkers controlled by Druj are often festooned with fetishes and similar items - especially shrunken heads and skulls. Whether this is part of the magic that controls them or simply to give them a more threatening appearance is unclear.
Marshwalkers can survive for only a few weeks away from the damp, fertile environments in which they live. Denied water or access to fresh vegetation and insects, they become brittle and begin to die. A marshwalker in this state is desperate and will stop at nothing to reach a safe location - they can inflict massive damage in their singleminded drive to find somewhere safe.
Marshwalkers in play
Due to the nondescript appearance of a colony in it's placid state, a human settlement can live near an area populated by marshwalkers for decades and never realise. There are many stories of marshwalkers rising out of bogs and making straight for new construction begun too near "their" territory; smashing the structures to pieces, and pulverizing anyone who gets in their way, before returning to the marshes and disappearing.
They are very sensitive to anything that threatens their environment. For example, when the Morass in Holberg was drained the engineers required constant protection from dozens of marshwalkers who strode out of the depths of the bogs and swamps bent on destroying everyone and everything responsible for the project.
A marshwalker is a major threat to a village, and several marshwalkers might threaten a small town. A well-equipped force of men-at-arms can probably drive a marshwalker off, but are likely to take serious injuries in the process. A lone character can easily outpace one, and might be able to come up with a cunning way to divert one, but one-on-one will likely be quickly dispatched.