Songs of Erui is my first stab at a D&D adventure path. I created it after I hit a snag running Scales of War and was really digging the story content for primal classes. I hit up Wikipedia for a crash course on celtic mythology, and quickly laid out a rough outline for a campaign that would ideally run my players from 1-30 over the course of 12+ adventures (extra encounters added to taste). The adventure path heavily emphasizes primal classes and races, and aside from whatever I could find on celtic myths borrows quite a bit from The Hallowing, Mythago Wood, and Lavondyss. CharlieAmra got me hooked on The Waterborn and Black God, which I began liberally applying as fast as I could after the fact: I'd done a lot of planning before I read the books, but its been extremely valuable stuff.
Songs of Erui takes place in a remote location in my implied world, called Erui. I'm really not sure where it is precisely located in relation to other areas (Arkhosia, Bael Turath, etc), as its the only part I've managed to flesh out so far (though in the story bible I keep mentioning that its somewhere north of the remains of Nerath, likely the northern-most part). During the rise and fall of the old kingdoms, Erui was kept isolated from discovery and conflict by a massive range of mountains, the Serpent Mountains. The mountains are so high, that it is said to climb them would allow you to reach the Astral Sea (havent decided if this is true or not).
Aside from their size, the other distinguishing feature is an old stone highway that passes through it, called the Dragon's Road. People who travel its length are never heard from again, and it is rumored to be inhabited by monsters or some form of old guardian.
Since no one actually knew what to expect, they created a bunch of random theories, the most popular of which that its a "forbidden paradise" of some sort, maybe like Eden or Nod. Really, I got this idea from Shadows of the Colossus, which also served as a very nice visual reference.
The real reason why people who travel through the mountains is that Erui resists mortal races, which I cribbed from Mythago Wood. You can try to go there, and you will be misdirected, probably suffer lots of terrible accidents like rockslides, and be met by extreme weather even when you shouldnt. If you can survive through it all, you might eventually find yourself in Erui (or just crapped back out into the northern regions of Nerath). The current inhabitants of Erui are mortals who made a pilgrimage there hundreds of years ago, or were there from the start (like dwarves, goliaths, and many fey creatures).
Even when you get there? It still sucks. The land itself is made up of hundreds of thousands of spirits that range in size and scope. Some inhabit a tree, while others are a large stretch of land. What they all have in common is that they do not take kindly to someone walking up and carving them apart. So, there's a long history of conflict between the spirits and mortals, especially the ones who try to build too much or tame the land. Sometimes minor spirits will kill a handful of humans, sometimes animals will overrun a farm, and sometimes a seemingly natural disaster will strike. Sometimes? A massive animal god shows up and just proceeds to ruin everyone's shit. It is because of this that shamans are valued: they can see and talk to spirits, making bargains and ensuring that they do not anger them.
Some humans take a more direct approach and just kill them, or find ways to weaken them with rituals before making the attempt (a necessity with many). Others make bargains with them, as some spirits dont mind if you kill the tree spirits that live on them, for example (they can be territorial). Hell, some dont mind being changed from one form to another, and many houses have very minor spirits living within them, providing protection in exchange for gifts of food and/or wine (they like the smell), and songs (each spirit has their own song).
The starting village, Dorsen, is a place that lives in harmony with spirits. The village is built within a circle of stone menhirs, and it is surrounded by groves of trees and farmland. They are very careful to take only what is needed, and gifts for spirits on specific holy days.
Songs play an important part in the campaign, and bards and shamans have default access. Singing a song specific to a spirit works in a similar fashion to a Diplomacy check, but is often used as part of a skill challenge to reduce the DCs, remove a failure, and other stuff that depends on the spirit, situation, and character. Its a pretty loose system that I like, and its prompted Josh to pick up shaman multiclassing so that he can call out the spirit in his sunblade, see into the spirit world, and better communicate with them. On the other hand, its also prompted Dave to start asking around for as many songs as he can in order to give himself an edge when it comes to dealing with them.
Here are the three Heroic tier adventures that I've planned. As written they can boost a party of five characters up to 11th-level. They are designed to introduce characters gradually to some of the key concepts that surround Erui in addition to giving them a sense of direction and purpose in the bigger picture of the campaign.
The Hydra's Grave (level 1)
The first adventure, this has the players tracking a band of goblins that are messing with farmers and shepherds around Dorsen (the starting village). Following the goblins, the party stumbles upon an old eladrin crupt on the outskirts of the Bone Forest. Mostly, this was a traditional dungeon crawl that allowed the party to get a few levels under their belts, learn a bit of Erui's forgotten history (namely the bard Morrigan and her three songs), and also start dealing with spirits (especially the Bear god).
The Hounds of Ulster (level 4)
After retrieving the remains of Morrigan, the party heads to Ulster in order to find a bone-speaker (ie, someone who can cast Speak With Dead) in order to ask Morrigan a few questions. Along the way they get attacked by undead in the river, as well as werewolves that are following them for some reason. Things dont go smoothly even when the party gets to Ulster, as the city is overlooked by an ancient castle and its ghostly king who ventures forth on full moons to hunt the populace. Unfortunately, timing is everything and the moon is almost full by the time they get there.
The Bone Forest (level 8)
With a new heading providing by the tormented ghost of Morrigan, the party mounts an expedition into the Bone Forest, a deadly realm that is haunted by fickle fey spirits and the mortal creatures that they've hunted and killed. The treasure they seek is one of Morrigan's three songs, rumored to have the power to force gods into an eternal slumber, which probably explains why someone buried it deep within a druid pyramid.