Saltmarsh in Hyperborea

In our Hyperborean campaign I've been adapting the AD&D 1st edition Saltmarsh series for Astonishing Swordsmen & Sorcerers of Hyperborea.

There's spoilers here for the entire series so if you're unfamiliar with the adventures and have reason to want to stay that way, you might want to hold off reading.

Alrighty... So the Saltmarsh series is marked by a series of discoveries:

• A "haunted" house is being used by smugglers.
• Those smugglers have been selling weapons to a group of lizard men alarmingly close to Saltmarsh. 
• The lizard men were kicked out of their original lair by sahuagin. Who also pose a threat to Saltmarsh...
• The lizard men have been assembling an alliance of aquatic folk against the sahuagin.

So how does this fit in Hyperborea? With its long winters, Hyperborea is a horrible place for cold blooded creatures like the lizard men. I posit they must go into a long torpor as their swamps freeze over. 

In the current 13-year cycle, these lizard men had barely awoken as winter ended but to find themselves under attack by the sahuagin. Like in the original adventure, the survivors escape to an older lair, one close to Saltmarsh.

AS&SH does not feature the sahuagin in its monster list, though reusing them from the 1st edition Monster Manual is easy. I was sorely tempted to change the sahuagin to deep ones, a nice Lovecraftian monster. However, when I think of them I think more of subterfuge. Of slowly taking over a town. That doesn't feel right for this adventure. 

I'd been flirting with the idea of using Hyperbroea's Atlanteans in this series - the original adventures feature an aquatic elf, a species not present on Hyperborea. Instead, I went with the idea that at some point in the distant past the Atlanteans genetically engineered some of their number, using long-lost science (indistinguishable from magic), to live underwater. 

One idea I got from the AS&SH Google+ group was to have the Atlanteans have made the sahuagin. This fits really well with my idea of aquatic elves being replaced by undersea Atlanteans. Perhaps, in an effort to protect themselves, perhaps from the deep ones, the undersea Atlantean made the sahuagin - an effort that was disastrous, creating their own worst enemy. One which also threatens the land as well.

Note - I found it interesting that Swords & Stitchery blog recently made a post about Saltmarsh as well - OSR Commentary On U1 The Sinister Secret Of Salt Marsh Adventure By Dave J. Browne & Don Turnbull For Advanced Dungeons & Dragons First Edition