Among the races of the Realms Below, dark folk are odd, because they don't really have A Thing. They have a gimmick—they’re fond of darkness and explode or otherwise cause mayhem when they die—but we don't know much about their aims, goals, or society.
Drow, for instance, are evil elves (gimmick) who live in matriarchal societies and worship demons (Pathfinder Thing) or an evil spider queen (D&D Thing). Duergar are vile dwarves who can enlarge themselves (gimmick) and slavers who serve a dark god of toil (Thing). Derro are insane, stunted humanoids who burn in the sun (gimmick) and abduct surface dwellers to perform experiments upon (Thing). Dark folk…we don't know. Even flail snails have more of a Thing (epic poetry!) than the dark folk do.
That starts to change with the dark callers. These dark folk lay priests are instrumental in summoning the otherworldly owbs, who in turn blanch the dark folk young and may even be able to alter their subspecies, in a circular ritual that pretty much guarantees some ancient pact or bargain was involved. The more dark callers there are, the more owbs are summoned; the more owbs are summoned, the more the race is shaped away from humanity toward some mysterious end state. So now dark folk have A Thing—but it’s still up to you to fill in the sketch of what that Thing is.
Interestingly, it takes three dark callers to summon an owb…and the owb, while free-willed, obeys the dark callers. So owbs might be agents of the dark folk’s Shadow Plane masters. But then again…maybe dark folk create the masters they need…
Here’s what I mean: With war looming, Joe Simon and Jack Kirby created Captain America, giving form to the gestalt hopes and aspirations of the American reading public. One could easily imagine dark folk society doing the same—only instead of an invincible Boy Scout, what if they created something far less wholesome? Driven underground by some cataclysm, maybe the Triassic dark folk sought to banish their terror of the darkness by embracing it. Maybe the first owb was summoned…or maybe it manifested out of the dark folk’s own need for a savior. Just a thought.
One more note before we get to the adventure seeds: Dark callers are also highly superstitious and ritual-obsessed. This might not come into play much if you’re running a surface dweller-focused, kick-down-the-bad-guys’-door campaign. But if your campaign spends a lot of time below the surface—say, in a Pathfinder version of Downer’s Oubliette or the Forgotten Realms’ Skullport—then dark callers might get enough screen time so that this fact becomes useful for GM role-playing and PC scheming. Also, it's a great excuse to use new/variant spellcasting styles—oracles, witches, summoners, or the new arcanists and shamans from the Advanced Class Guide all come to mind.
At night, Devon languishes in darkness. Several colliers have recently been murdered, and the charcoal fires in their huts have all been put out. The Lamplighter Guild’s members have all left town, save for one man drowning his sorrows at the Trout & Tankard. A dark folk clan lives directly below Devon, and a zealous dark caller is directing his minions to make the nighttime streets lightless by any means necessary.
When a favorite dark dancer dies during the Feast of the Moth, a dark caller reads the signs and believes the clan must be purified by the burning cold touch of an owb. She and her apprentice are not enough to call the dark spirit, however, so they make plans to abduct a conjurer or summoner who can complete their circle.
“Fear the white elf; the gnoll follows one step behind.” So goes one dark caller superstition—and dark folk may honor or murder the elf as a precaution. It is bad luck to harm a ratfolk, but nor will a dark caller touch one. Signs may be read in the liver of a blind cave lizard or a troll. Mushroom stalks may be used to cast hexagrams from the Book of Elements; adventurers attacked by dark folk in a mushroom forest are usually guilty of treading too near such sacred fungi. No dark caller will shadow step in the presence of a black cat, changeling, or fey, for fear that a hag may follow him through the black portal. And the blood of a dwarf woman cleanses all sins, according to many dark callers. If adventurers are called upon to rescue such a maid, they had best act fast.
—Pathfinder Bestiary 4 42
Owbs also apparently hang out with doppelgangers. This is super weird and unexpected and I can't wait to explore this once we hit the letter O.
I originally wrote, “One could easily imagine a fascist or communist dark folk society doing the same...” because not every evil society has to be about dark gods and Great Old Ones, and because I kind of love the idea of dark folk shaping themselves out of sheer civic drive. Then that got me off into a tangent about how yes, I know these ideologies are on polar opposite ends of the political spectrum, but that the methods they employ in terms of social control and propaganda are often nearly identical. But that then required me to clarify that I’m talking evil, oppressive, Soviet-style communists, not your local food coöp communists—those guys are awesome. (Except during zucchini season, because no one can eat that much zucchini.) And that tangent drove me to tell you that if you’re ever in Baltimore these guys are worth looking up. And then I realized that once I’ve spiraled so out of control that I’m recommending radical semi-anarchist coffee shops that are not within easy driving distance of most of you, it is probably time to contain all of the above in a note way down out the bottom. Which I have now done.