Completed Ytarria Hex map with terrain added

[Pursuivant]

Far up-thread, I posted some ideas on how the plains areas could hold African-themed cultures and fauna, including alkaline soda lakes. They tend to occur when water features blend into desert areas.

Mildly acidic swamps are realistic due to the presence of peat layers, but but the acid swamp from Orcslayer is pure fantasy, with acid-adapted monsters and water pH low enough to quickly cause burns.

Given that some of the soda lakes in the Rift Valley are high enough in pH to slowly cause damage, a modestly acidic acid swamp (e.g., about as strong as strong vinegar) wouldn't be that much of a stretch, if you could come up with a suitable cause.

One possible explanation is that the swamp area overlays large petroleum deposits, which off-gas hydrogen sulfide, which percolates through the swamp water to produce sulfuric acid. In most places, the water isn't that acidic, but in areas with the most hydrogen sulfide the acidity can get dangerously high such that it causes slow chemical burns. Over time, the local flora and fauna adapted to the acidic environment, filtering out acid when taking in water with the effect that pH gets really low to the point that there are areas of near-pure acid.

Or, you could just say that the acid effect is magical; either an effect of the Banestorm or the result of some dark magic happening deep beneath Yrth's surface.

Where you've got corrosive liquids, the underlying rock needs to be inert enough to prevent reactions from happening which would create caves and cause the corrosive to leach into the ground.

I like the idea of an old meteor crater in an area of relatively inert rock which created a depression. This area gradually filled with massive amounts of clay to hold the water in, except in cases where there are hydrogen sulfide seeps.

In areas near the swamp, you could have amazing caves due to hydrogen sulfide action. The same area might have petroleum seeps and methane blowouts, including places where the methane has been set on fire, creating natural "eternal flames" or "hell gates."

Edit: The fact that the acid swamp borders a major river system argues against large highly acidic areas, since the acid would tend to be diluted. The presence of a river system means that you could have extensive wetlands, however, like the Pripyet Marshes or the Everglades. That would seriously complicate humanoid expansion from the eastern part of the continent to the western area. If you like the idea of hydrocarbon-based hazards, Out In The Middle of Nowhere is also a good place for any obvious coal or petroleum deposits, since they'd be massively exploited if they were any closer to civilization.