An area in my campaign setting. My own derivation of Lovecraft’s ‘Blasted Heath.’
In the middle of a field of stone and dirt, on the outskirts of a once-green forest, is a decaying cavity in the earth. Shaped like a bowl, with a rim slightly taller than the surrounding flat land, it is over three hundred feet deep in the center and over a thousand feet wide at the edges.
The ground and dirt in the bowl, and spreading up to half a mile away in all directions, is sickly gray. No vegetation grows in this radius, and outside of the radius for up to three miles, all plants take on unnatural hues. The forest slightly to the north decays – the leaves on the trees die as they sprout, covered in red and yellow pulsing veins. The trunks bubble a viscous brownish-orange fluid from rotting hollows, vomiting their putrid filth from within.
No animals live within five miles of the crater, and no humanoid settlements have been attempted for centuries, despite the close proximity to caverns with skarns of magi-precious gems such as malachite and andradite.
None know when the hole in the earth was formed, or from where it came. Its origin is a mystery to all who are alive today, perhaps save the eldest Aedryn or Urshael. It has existed since Vaarol, the Orchid Realm, was nothing more than a fishing village along the edge of the Tare, back when the Tare flowed mighty from the jagged peaks of the Kholdera Mountains, instead of in the muddy trickle it is known for today. It has been known of since before the Aedryn and the Urshael retreated beyond the Kholdera Mountains, so though many a crooked-toothed old man will say the hole was left by those mythic creatures as a penance or weapon against the humans, those who have ever bothered reading a book know it not to be so.
Some sages who have studied the hole (which is known in the scholarly world as the Wasting Wael) have found evidence that the walls of the depression were blown outwards, as though a magical explosion beneath the surface of the ground caused the crater. Others say there is clear sign that this is nothing more than the location of a fallen star, and that there is plenty of evidence that meteors and their like have many times landed across the planet in much the same way.
Other more fantastical explanations describe the hole as having been scooped out by the giant hands of some ancient, primordial titan, who even now slumbers beneath the land. Still others believe there is proof that the hole is getting deeper (this is not the case), and that the very earth itself is melting in this poisonous recess.
Whatever the reason for its existence, there is very little to explain the deadly effects of the toxic soil all around. Soil so toxic that travelers have said their very boots have deteriorated on their feet, and horses have fallen lame while traversing the land around it. Birds go out of their way to fly circles around the Wael, and no animal familiar with the area walks across the gray, rotten loam.
Any living creature that spends more than four hours on the dirt of the contaminated area (basically anything within a five mile radius of the hole) must roll a save vs poison/fortitude (Very Hard DC if applicable). Anyone who fails immediately begins to waste. The first signs of this are their extremities begin to ache, followed by turning gray within 1d4+4 hours. Saves are made every 2 hours after the initial, with the DC increasing by 2 every time. After the 1d4+4 hours, the wasting is at a point of no return, which may only be cured by a high level priest casting Remove Curse, Remove Disease, both at Extremely Difficult DCs (30 for 5E). During this time, the being loses 1 point of Constitution and 1d4hp every hour, until either Con is 0 (in which case, the being dies and decomposes into a mess of gray goo), or hp is 0 (in which case, the being dies and becomes a Waelwraith).
All DCs are increased by 5 if for some reason, the unlucky creature was within a mile of the center.
Several days after dying of the wasting sickness, the creature may return as a Waelwraith, a special undead. These undead will haunt the place where they died, attacking violently anyone who comes within a dozen paces of their death spot.
Looks like a shriveled, gray version of the creature who died. Hair falls out soon after rising, and the extremities of the skin rot off soon after.
HD 5 (hp 20 – 25), Defense – as leather, choking 1d6/round, Special: centered on Waelwraith, 5′ radius, aura of wasting. Save poison/fort DC 15 or take 1d4hp & 1d4-2 Con damage/round until successful Remove Curse at DC 20. 0 Con or hp is just death, no rising as another Waelwraith.