"In the in between lands of the northern and southern territories, where the air is humid and the ground wet, places with decay and rot. Around these locales a strange form of insect lives which is capable of re-animating those who have been left out on the bare ground to die. Throughout the history of the people who have lived there, there are storied accounts of people coming back to life, and by all accounts these resurrected people rarely are benevolent, and are more seen as people brought back to life to seek revenge upon the disrespect they faced before and during their death. By some accounts, these creatures can be turned by making right the wrong they faced, such as if the reason they are there is an improper burial, one should cremate something that represents them or belonged to them. However this only applies if one sees only one of them, and in many cases there can be more than a few, in which case it is more likely that these creatures are here to seek revenge and not an ultimatum to their existence.
However in most of these cases the reason for these people who move in the swamps and wilderness is not due to something spiritual or religious, but it is due to a strange insect. This worm like bug can re-animate and take control of corpses that it finds, though smaller varieties are more common than larger ones that can re-animate whole dragonoids. This is because they grow inside their hosts and when large enough, they will find a larger host creature to take control of. It has been noticed that sometimes they can even take control of those who are not even dead yet, for instance in cases where the person is incapacitated or unconscious. This is also a good reason why you always should rest inside a hammock rather than inside a tent when traveling through these rot woods, if not just for keeping your backside dry, then to avoid these things and all the other skittering bugs that live there.
They seem to crop up here and there every now and then and larger infestations happen sometimes, but they also disappear quickly enough, they cannot keep up a large population as they need dead creatures to thrive, so sometimes they may seem they have gone extinct, but after events where many people or creatures perish their population may flare up suddenly. While disturbing, they are not terribly dangerous to an adventurer with keen eyes, an engorged abdomen, inability to speak and overall haggardly appearance are the most telling clues, however as stated before, sometimes they take control people who are still alive and in these circumstances it becomes slightly more trickier as they supposedly can still speak. They will act somewhat unpredictably and while seemingly lucid will now have become overly protective of the thing inside them and more often than not, if not left alone, they may turn hostile."
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