Roughly inspired by stories from the Solomon Islands, adaros are shark-men with a mystical connection to storms. Nomadic, they might attack nearly anywhere in the ocean at any time—often when sailors are already overwhelmed simply fighting the elements.
Adaros are similar enough to sahuagin that it might be hard to decide when to use one or the other. Both love sharks and get along poorly with other races. However, though violent the lawful sahuagin are empire-builders and long-term planners, often religiously minded and skilled at espionage as well. Adaros are nomads and barbarians, seen by sahuagin as rough larger cousins whose visits are tolerated…for a time…until they can be directed elsewhere—preferably toward the sahuagin’s many enemies. Their religion is more animist as well, revering storms as entities in and of themselves rather than worshipping a stable pantheon or state deity. And while sahuagin adore and respect sharks as pets and even totems, adaros practically are sharks.
Grounded upon a reef, seafaring adventurers have a chance to set their ship free two days hence, when a confluence of full moons causes the tide to rise higher than usual. But as the moons wax a storm system blows in, bringing raging adaros cresting along the rushing waves.
Poisoners and thugs travel to Urchin Cove to procure poisons that can stand up to the rigors of land and sea travel. There adaro rogues, rangers, experts, and alchemists tend pufferfish and ply their venomous craft. It is custom that every visitor to the cove must dodge or survive the spear strokes of at least three adaros without showing fear before the chemists will even think of selling to him or her.
The coming of literacy and wizardry is changing Vornveg. The newly crowned king wishes to call an Althing, but a rogue sect of priests who worship a violent interpretation of Thor have sworn to stop the gathering. They rally adaros to their side to stop the longships from ever reaching the rendezvous.
—Pathfinder Bestiary 3 7
I’ve mentioned this before, but if you’re serious about aquatic adventures I’d recommend checking out the article “Oceans of Golarion” in Pathfinder Adventure Path #56: Raiders of the Fever Sea. But ignore the title, because my advice isn’t just for Golarion fans. Pathfinder fans in general and even 3.5 GMs while appreciate the expanded wandering monster table, a list of locations to visit on the Plane of Water, and most especially the breakdown of the 16 main aquatic races and their habits, alliances, and enmities. A lot of the aquatic races tend to blur together after a while, and this guide is your one-step cheat sheet for quickly telling them apart.
(Here’s a test: Off the top of your head, can you explain the differences between the adaro, ceratioidi, iku-turso, and siyokoy? Follow-up question: Now do it without once mentioning the animals they most closely resemble. I totally fail both tests.)