The Aquillus, an aquatic people primarily dwelling underwater but capable of surviving on land for short periods, comprises two distinct subgroups resembling separate races. The Kul-Matsya, thriving in cold waters, boast physical prowess, towering over their sleeker and faster counterparts, the Yrm-Matsya, who prefer warmer waters.

Friction between the two groups is evident: the Yrm-Matsya follow the religious teachings of the Deep One, a deity bestowing formidable abilities upon its chosen followers. This relatively new religion emerged after the Great Undoing, reshaping not only the surface world but also the realms beneath the seas. It arose as an answer to the darker world that emerged during a changing time.

In contrast, the Kul-Matsya adhere to the ancient teachings of the Order of the Salio, a dwindling religious faction resisting the dominance of the Deep One’s worshippers. With each passing generation, this rival religious power supplants the once-preeminent philosophy, diminishing the influence of the Kul-Matsya. Today, this power imbalance grants the Yrm-Matsya greater political sway, often relegating the Kul-Matsya to the sidelines.

What unites both groups is a shared cultural tradition of raiding the surface world for treasure and slaves, deeply entrenched in their society. Warriors who return with loot from the surface are highly esteemed, often elevated to positions of leadership. Most raids target Protectorate villages and towns, leaving them ravaged. However, anyone in the right circumstances could be considered a target, as the surface world is theirs to prey upon.