A long time ago a powerful tribe settled near the place who would become the thriving city of Asta, when the colonist from the old world came to settle in America. This tribe was not famous for the many hunters or the riches, but instead for the high number of shamans and healers, adept in the use of magic tied to the natural world.
Many of them were the so called skinwalkers, capable of assuming the form of an animal at will to commute better to nature, as their culture gave much significance to spiritualism. For hundreds of years this populace held dominion over the region, more often than not declaring their neutrality in the various tribal conflicts between the neighborhood, until the arrival of the conquerors beyond the sea.
Those new settlers saw the magic of the natives and declared the practice an affront to the natural order, and sought to erase from history the tribe. In time the natives would scatter to the four winds after their defeat, but not before their magic seeped into the surrounding woods and soil after all the time they inhabited the region, forcing the invaders to isolate the surrounding territory in fear that somebody could stumble in one of the magical hotspots.
In the last years of the conflict the shamans placed many spells to neutralize the aggressors without resorting to murder, and no one was very thrilled in the opposing side to be deprived of their normal body, to end up joining the ranks of the barnyard animals or woodlands critters if they accidentally sprung a trap. The most protected places were of course the homes and the religious sites, and while the magic on the tents dissipated harmlessly after their destruction the supernatural spell in the traps and burial grounds persisted through time, particularly because the curses could be recharged automatically after the first uses.
The denizens of the nearby city of Asta learned quickly the telltale signs of old snares and dangers, and this knowledge was transmitted from one generation to the next as time passed. Everyone in the village knew to never intrude in the ancient grounds, with whispers about ghosts, disappearances and strange noises in the night and even the conquerors were hesitant to challenge the lingering power of the tombs. Of course, the vacationers coming from far away never heard about the haunted section of lands, and most of the ones who heard the rumors dismissed them as useless superstitions.