Seep Eco-gnomics
So, I went to see Harry Potter last night. Good film.
But after, the pal I'm with says, "What's with the thousand year old bathroom with Victorian fixtures?"
"Magic," I say. "it's not like there's real plumbing there anyhow. If you want to update it, you just wave your wand and say "Johnnus Redecoratum" or something like that and all the fixtures reconfigure. They're all just portals to the Elemental Plane of Sewage, you know."
And then we give each other a significant look and I add, "I didn't just say that."
"Demi Plane of Ooze between Earth and Water, as I recall," he adds. "Or is that quasi?"
See, the problem is, surface dwellers have it easy. You want to build a privvy, you dig a hole in the ground, and after a while, you muck it out and manure a field with it.
In the Underdark, there aren't any fields, and finding a spot to dig a deep hole that doesn't wind up causing complaints from hostile downstairs tenants is a pain. And you can't even burn the crap, excuse the expression, because most of the inhabitants of the underdark are carniverous, and carnivore dung makes lousy fuel.
So, naturally.
The reason Akin's Seep is a popular crossroads is that it's got the only clean privvies for miles. Fathoms. However you measure these things in the Underdark.
Bit tricky making one way extraplanar portals, but somebody managed it.
Nice deal is, if you've got pipelines, you can charge folks to drain their caverns. Not just a crossroads, more of a confluence.
And suddenly, you've got a nice little politcal leverage to avoid getting conquered by one Underdark Empire or another. Too valuable to put out of business, and nobody really wants to own you. A free market, indeed.
Until you've got a whole lot of undead walking around who don't give a crap, as it were.
Let's hope Somebody never had to deal with any Elementals.
