- Semi-intelligent humanoid - Orcwort
- Undead - Graveyard Sludge
- Giant/ogre/troll race - Fomorian
- Great wyrm or lizard - Fiendwurm
- Something aerial - Windghost
- Something to lurk in the water - Ocean Strider
- Something from another dimension - Arcadian Avenger
- Ancient fey - Banshrae
- Classic mythology- Maenads
- Underworld - Living Blasphemy
The Green River, Dancing Jungle, and the Mountains of Sin
The region was first settled by the ancestors of the fomorians, long before they were driven into their mountain caves and away from the sun. They are barely clinging on now, and the ruins of their cities and canals and plantation farms can still be seen in the lowlands along the Green River.
It's dangerous to go much further than a mile or two from the riverbank: the wilderness is overrun with orcwort trees (an invasive pest species, but also a primary food source for human settlers on the Green River.) Furthermore, the thick forests are mastered by the banshrae and their maenad consorts. Locals know from their earliest childhood know how to close up their ears with beeswax, to drown out the daemonic whine of the pipes and the rhythmless thumping of distant drums that dictate the endless dances that have given the region its name.
What caused the creation of the living blasphemies is lost to time - the fomorians might still know, but they do not seem ready to confess their ancient sins to the world. They emerge in the deep jungle sometimes, in the old ruins and in the caves deep below and up in the mountains. The emergence of a blasphemy brings shortly with it an arcadian avenger, or several, to strike the manifested sin down. They do not care to avoid collateral damage, and have no real desire to interact with the human settlers. They don't even seem to care all that much about the fomorians, perhaps believing that they in their inbred decline have already been punished enough. The god or gods they serve go unnamed and unspoken.
A secondary effect of the blasphemies is the raising of the dead - anyone interred in the soil or left alone is raised as a graveyard sludge after a swift cycle of decay. Cremations are the order of the day, on pyres filled with grave goods made of the purple, papery dried hides of the orcworts.
Reaching the settlements on the Green River, or leaving them for that matter, is an increasingly difficult task. Several clans of ocean striders have taken up residence on the reefs around the Green River's mouth and have proven quite belligerent to all sea travel and trade, unless sufficient gifts and tribute are provided to them.
There is a fiendwurm up in the mountains, tainted perhaps by the same sins that form the living blasphemies. It certainly doesn't complain about the tribute that the fomorians give it, but what it really wants is an archpriest. Someone ought to go steal one.
The windghosts that live in the skies above the riverlands are significantly more colorful than their bleaker northern cousins. They swarm above the river during their mating season in the late spring, inspiring the raucous and debauched Festival of Kites, the start of the riverlander new year.