Devil's Fall
This area was once part of the Riverwild, but was contaminated by abyssal energy upon the death of a Hezrou lord summoned by an adventurer as he fled an angry dragon. The abyssal blood released by the hezrou's death spread throughout the landscape and melded with the nascent fey energies of the forest to produce a Swamp Blight, a type of sentient and fervently malign ooze, which claimed dominion over the forest-turned-swamp.
This usurped the claim that the Kingdom of the Green had on the area, and the once-beautiful forest swiftly became sodden and fetid, large swarms of blood-sucking insects began to hatch from the Blight's oily mass, and over time the swamp began to spread, the Blight pushing its domain ever-outwards.
The Green Man and his followers within the Court of the Green attempted to stop the spread and slay the Blight.
The Green Man melded with the forest within the Green Man's Heart to keep the spread in check, and left his severed right hand as a powerful talisman of the forest's might for his followers to use in an attack upon the heart of Devil's Fall, in an attempt to slay the evil causing the corruption.
The attempt failed, with all of the attacking force but Sen'do perishing in the attempt. Since then, the Green Man has been trapped underground, in an unending struggle to keep the blighted swamp from claiming more of the forest, while his consort the Heartmother attempted to keep the court stable and the forest protected from within her court at the Temple of the Green.
Fauna & Flora
The forest-turned-swamp has few successful native species. Wolves and a few prey species have managed to survive in the area, but they are in turn hunted by the new residents.
The nests that spawn Boil Imps have infested many of the trees throughout the swamp.
Insect species have exploded in population and become twisted in form due to the abyssal influences of the Swamp Blight living at the heart of the region.
The Blight's influence has caused any creatures who die within its influence and are not immediately consumed to rise as Bog Mummies. While they do not feel an urge to feed on flesh, they have a tendency to attack living things that wander too close and are still dangerous even while quiescent due to their drowning aura - animals can be found having suffocated simply from running into a patch of swamp containing a dozen bog mummies lying in torpor underneath the water's surface.
Two new apex predators have taken over, twin black dragons. Their relationship with the Swamp Blight ruling over Devil's Fall is unclear, but was likely friendly to some extent, as their lair was less than two miles from the Blight's.
[Update: Both the blight and the dragons have been slain by adventurers, though many bog mummies remain within the waters of the swamp.]
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