Disclaimer, I'm not very good at making races, so if you think something isn't up to par, just let me know. Or you could just deconstruct the whole thing and re-create it...whichever you find easiest.
Name: Mer People
Detailed Description: They are a large race compared to many of the other traces, slender and strong, they are rulers of the waters. There are four branches of this race each being identified by the structure of their lower torsoes: fish tails, octopus tentacles, seahorse tails, and jellyfish tentacles. Each of their torsoes average 3 feet in length while tail lengths vary from each of the divergent tail types. Octopus and fish tails vary from 4 to 6 feet in length while jellyfish and seahorse tails vary between 3 to 5.6 feet. In addition, seahorses have wing like appendages on extending down their backs from their shoulder blades to the middle lower portion of their backs. These wings extend between 1 to 3 feet in length.
Octopus and fish torsoes are very round in shape, their shoulders sloping down rather than having the usual squarish shape of land dwelling humanoids. This allows for high speed swimming for both species. The Jellyfish torsoes are very frail looking while being almost as rounded as those of the above mentioned. Seahorse shoulders are very square and ridged compared with each of the other species. The last two species mentioned are by far the slower beings of the seas.
Each of these species has distinct ears which correlate to the animals we know here on earth. Those of the octopus are none existent and are unseen, those of the fish are the color of their tails and tend to be fins which extend around an opening for the ear, those of the jellyfish are made of the same material as their torsoes being fluid and rather than hearing, they detect pulses in the water but are able to hear sounds in addition, those of the seahorse are much like the wings which extend from their backs being fluid rather than a fin like structure. These species have a radiant array of colors which are possible for their tails, hair and ears. Their torsoes are a pale extention of their tail colors turning into a almost lucid white.
History of Origin: Mer Folk believe themselves to be born of the water element’s jealousy of those elements which had interaction with intelligent beings. It stole land dwellers, drowning them in water and breathed new life into them with no memory of their lives on land...
There is no real historical data on mer people as no one had payed much attention to those being which live beneath the surface of the waters.
Other races believe the mer people to have come from the dark recesses of the unknown waters, being a cursed and evil race.
Specialties: Each of the species has a physical trait which allows them to breath under water and they are able to hear things in a 2 mile radios. They are up to 2 or 3 times strong than any human when in the water/in their natural habitat.
They also have the ability to transform into a land dwelling creature once a day for a limited time; however, they must constantly drink water, they are unable to travel in the sun for extended periods of time or in extreme heat/cold, and upon the limit of their exhaustion in land dwelling form, they must return to water or else die. While on land they are extremely weak and very susceptible to any form of magic which disturbs the moisture in the air. If it is a rainy day and there is plenty of cloud coverage, they are just as weak but they can stay in land dweller form longer.
Combat: Mer people find weapons to be hinderances in combat under water. The octopus and fish tailed individuals enjoy a good fight and are more apt than either the jellyfish or seahorse type who shy away from fighting. The latter are very docile in nature as opposed to the two other types who are very dominate. The jellyfish and seahorse tend to have more magic potential than teh other two and are very willing to use it to ward off any fight which might occur.
Alignment tendencies: They have tendencies to be anywhere from neutral to neutral evil; though, in their society they believe themselves to be completely neutral with a tendency for maliciousness (especially when it comes to land dwellers). They are willing to do just about anything for their own benefit and if that means someone has to die, then so be it. When it comes to land dwellers, they are very playful and they often find that land dwellers are prone to death in their play.
Climate and terrain: Water, that’s what they need/must have. They exist in the deep cold recesses of the ocean and in the warm shallow waters of the tropics. If there is water any place all year round, don’t be surprised to find a stray mer folk residing there. While on land, they prefer to completely avoid combat as they are so weak, but if they can draw their opponent into the water then they are more than willing to get into a good spat.
Family/Organizational Structure: They live in a pack like structure, where the strongest or the one with the most power among them rules till they release their position or until another takes their place. It has been heard of that a jellyfish or seahorse type have ruled over a clan of mer people because of their great magical abilities, but it is far from the norm. If one is unable to hold their standing within the clan or provide for it’s good in some way, the clan is keen on getting rid of the nascence whether it be through death or the individual fleeing to be an outcast.
Other Info: The average life of an individual is about 50 years, not including those whom are killed at an early age. They develop and grow at a very fast pase with childhood only lasting about 5 years. Children are raised by the weaker of the clan who are not allowed to have children for fear of infesting the clan with weakness. There are some instances which defy this norm of a 50 year life span... if a single individual departs from the clan, having little to no encounter with them or others of their race who wish to challenge them, mer fold have a potential of living indefinitely. Their life source/Immaterial magic is able to replenish itself, allowing for almost an eternal life, but this requires a life of dedication to the water element.