The Arkos

Port Ffirst has become a burgeoning dock town with multiple quays and a nearby beach resort, but it has had a difficult road reaching this prosperous state. In fact, it was at one time completely abandoned and left in the swamp shortly after it was first built. There were just a handful of houses, a lumber mill and a shipyard, and then they were invaded. The whole operation was overrun by a Grung raiding party, sailing into the harbour on light sailing craft in the night. It took the concerted effort of adventurers to push the Grung out of Port Ffirst and claim it on behalf of a merchant named Kensington.
These Grung were members of the Arkos - a particularly expansionist tribe native to Kantas, who are understood to hail from across the inland sea, on another part of the continent. They are named for a particular kind of deadly poisonous flower found elsewhere in Kantas. The group that Daring Heights and Port Ffirst have encountered are a warband tasked with expanding their influence and territory to the other side of the water. After being driven into the swamp to the north of the port, they mounted a campaign to claim the rest of the swamp from the Bullywugs who lived in the northern half of what came to be known as The Frog Bog.
The Arkos are fierce warriors, strong in battle tactics though light in wider strategy, utilising their poisonous skin to its full adventage, though the local Bullywugs were a very formidable foe, especially given that they had tamed and bred a cavalry of large spiders which was off-putting for even the bravest opponent. This particular war went especially poorly, when a Slaad emerged from the nearby sea, drawn by the chaos of their warfare, and took violent command of the Grung forces, demanding they attack again and again for months. When the Slaad was eventually defeated (adventurers again), the Grung and Bullywug alike were in enough need of rest that the fighting ceased. There exists an increasingly tenuous truce in the swamplands now, the Bullywug unhappy that they did lose much of the bog to the Arkos and they in turn angry that they have not completed their mission to conquer the whole swamp. With Port Ffirst increasing in strength daily, this is a real problem.
In the meantime, they stay mostly in their warcamp, which is a relatively orderly place amongst the fetid pools and half-dead trees. An Arkos warcamp is difficult to spot as, being naturally proficient in jumping, they tend to make their camps high up, in this case in the willows and other trees of the swamp. A trained eye would spot suspended tents made of strange hides, likely from creatures on the other side of the continent, and large sections where a piece of wood has been carefully anchored between tree branches to give platforms for gathering, training, cooking. As they can only have two or three such places in any camp, the Grungs are disciplined in their usage of them to ensure that everyone has the opportunity to make use of them for their needs.
Among their own kind, or among established allies and friends, they are both welcoming and encouraging. As soldiers they are more congratulatory than admonishing during training and many have a positive demeanour that some newcomers find jarring with the military focus of the camp. Their drive to conquer is less from a grand strategy about resources and locations of geopolitical importance, and more a simple, deeply-held belief that the world is theirs and they simply have yet to claim it directly.