If naga are the exclusively terrestrial counterpart to the amphibious medusae, the merfolk are the exclusively aquatic counterpart. Their cities are spread far and wide in the Aarnian seas, but their largest population settlement is in the Great Barrier Sea, a nearly impassible sea between western Zenninfal and the peninsula of Jerohm on Yessha.
Merfolk are a race of creatures who closely resemble humans from the torso up, with gray skin, longer pointed ears, and rows of gills running down their backs. At the top of their head, hidden by hair, they have a third nostril that acts as a blow hole. From the waist down, they have a body the shape of fish, with a fin parallel to their shoulders, like a dolphin. Merfolk are typically 5-6 feet long from head to tail, and typically weigh between 120 and 200 pounds. They have lifespans slightly longer than humans; the average age of death is 90, and merfolk have been known to live to 140 comfortably.
Merfolk are mammalian and require air to breathe, but with the gills on their back complimenting their respiration they have an extraordinary lung capacity and can spend days without surfacing, though their ocean-floor cities have carefully designed air pockets, replenished by biological technology.
All of them have access to psionic elemancy, despite their spiritual element type, and they use these psionic abilities exclusively for their language. This psionic language is verbal however, and while they can project their language into the minds of other godtouched, said godtouched need to learn the language to understand it. Blessedly, many merfolk have additional psionic elemancy skills that allow them to easily learn and understand the spoken languages of other creatures.
Males tend to have very long, white beards and hair that tangles up around their faces. When swimming, the hair helps channel the water around them into a sleek shape. Females have no beards, but their hair flows down over their back gills protecting them and acting as a filter for the water. They reproduce as fish, spawning in the water - however, the female will retrieve many of the fertilized eggs and then incubate them in her body. Her womb is actually somewhat hostile to life, ensuring that only the strongest merfolk survive to be born. It is not uncommon for all the eggs in a pregnancy to die due to these conditions, but spawning is frequent.
As an interesting side-note, magical experimentation has suggested that the females are in fact genetically male, and produce the sperm and not the eggs, even though they appear female, have female characteristics and give birth to the young. This would of course mean that the males are genetically female and produce the eggs.
Merfolk society is arguably the most successful on the planet. They are the only godtouched race to have a genuine industrial revolution, and they have access to technology that those on the surface could only dream of. Their mastery over civic planning, artificial life forms, weapons, genetic engineering and using these talents to improve their standard of living is second only to the demons in the astral plane. Their technology is organic-based however, and is not immediately recognizable as technology. Surface dwellers will often mistake the tools and weapons of the merfolk to be a kind of biomancy, but it is in fact not magical at all. For instance, merfolks have laser weapons that look like organs that strap around their wrists, and the flagship in their navy, the Leviathan, is thought by surface dwellers to be an actual, natural born sea creature.
Effects generated by merfolk weapons, while similar to magic, are not susceptible to magic resistance and are quite deadly, so a violent encounter with them is very dangerous and almost requires magical shielding.
Culturally, merfolk put an emphasis on strength, not just physical, but emotional and rational as well. The strong rule, and a ruler ceases to be strong when their policies do not benefit the merfolk race. This dogma has been drummed into them for millennia by Occus, their progenitor god, and he still takes quite an active role in their society. He helps ensure that their many ocean cities run smoothly, and he is responsible for the merfolk's current isolationism. In centuries past, merfolk were known for committing bloodthirsty genocide on all the other aquatic godtouched races. The only survivors were the medusae and aquatic dragons, who were not directly targeted by the merfolk armies. Despite having the power to rival humans, and perhaps claim the land of Aarn, the merfolk and Occus in particular view it as too costly a battle, and consider the current holdings of the merfolk to be adequate. Merfolk do not tolerate intruders into their oceans or their society and often act with deadly force, though adolescent merfolk often visit the shores of Aarn to satisfy their curiosity about humans.
There are many different subraces of merfolk, but I will not go into detail here, because even for a complete game rulebook such knowledge would be far too esoteric to be useful. Some traits that exist however in merfolk subraces are green or blue skin instead of gray, longer, pointed ears, finned ears like a fish, webbed hands, long flowing fins growing from their hips or back, and one merfolk subrace even has twin antennae on their forehead that glow, like an angler fish.