Also Known As:

Merrow, sea-maiden, sea-nymph or merman. 
Other races, Selkie, Kelpie, Naiad, Nereid, Nix, Undine 
Historically there has been belief in part fish and part human creatures for thousands of years. The first references to these creatures is in the form of the God Oannes, who was the lord of the waters worshiped at the beginning of civilisation in ancient Babylon. There are several other fishtailed gods, but the classic mermaid known in Britain, is more likely derived from Celtic legend, folklore and local sea lore, in places where people were in contact with the sea as part of everyday life.

Physical Appearance
Merrow (from Gaelic murúch) or Murrough (Galloway) 
Is the Scottish and Irish Gaelic equivalent of the mermaid and mermen of other cultures.
These beings are said to appear as human from the waist up but have the body of a fish from the waist down. They have a gentle, modest, affectionate and benevolent disposition.
There are other names pertaining to them in Gaelic: Muir-gheilt, Samhghubha, Muidhuachán, and Suire. They would seem to have been around for millennia because according to the bardic chroniclers, when the Milesians first landed on Irish shores the Suire, or sea-nymphs, played around them on their passage. Female Merrows were considered very beautiful, whereas the mermen in their true forms were ugly, another reason why Merrow women sought out human men.
What is known of them is that while immersed in the waters their hips are scaled, and those curves end in a long and flat-finned tail of varying and often beautiful coloration. They can swim near as swift as a lean-built porpoise, but rarely reach such speeds for anything but joy's sake, the Merfolk having no natural predators in their waters, able to both outstrip and outsmart even the Sea Serpents of legend, or so it is said. When Merfolk find themselves on land, their scales gradually recede, their long tails forming a pair of long and usually delicate legs.

Scottish mythology tells us Ashrays, or Water Lovers, are completely translucent water creatures that are often mistaken for sea ghosts. They can be both male and female and can be found only under water. Being completely nocturnal, one would never come across such creatures during the day. When captured and exposed to sunlight ashrays supposedly melt and only a puddle of water remains.

Is a creature of Irish folklore roughly translated into "water hound." It resembles both a dog and an otter though sometimes is described as a half dog, half fish. It lives in water and has fur with protective properties.

Finfolk (sometimes Finnfolk)
Are sorcerous shapeshifters of the sea, the dark mysterious race from Finfolkaheem who regularly make an amphibious journey from the depths of the Finfolk ocean home to the Islands. They wade, swim or sometimes row upon the shores in the spring and summer months, searching for human captives. The Finfolk ( both Finman and Finwife ) kidnap unsuspecting fishermen, or frolicking youth, near the shore and force them into lifelong servitude as a spouse.

Is a supernatural water horse from Celtic folklore that is believed to haunt the rivers and lochs of Scotland and Ireland; the name may be from Scottish Gaelic: Each Uisge, cailpeach or colpach "heifer, colt". In mythology, the kelpie is described as a strong and powerful horse. Its hide was supposedly black (though in some stories it was white), and appeared as a lost pony, but could be identified by its constantly dripping mane. Kelpies were said to transform into beautiful women /men to lure mortals into their traps. They created illusions to keep themselves hidden, keeping only their eyes above water to scout the surface.

 ( làbh-allan, la-mhalan or la-bhallan). is a mythological creature from northern Scotland.
It was generally considered to be a kind of rodent, and indeed the name "làbh-allan" is also used for a water shrew or water vole in Scottish Gaelic. It was however, reportedly larger than a rat, very noxious, and lived in deep pools in rivers. Its poisonous abilities were legendary, and it was said to be able to injure cattle over a hundred feet away.
There are claims that  should you preserved the skin, it can be  used as a cure for sick beasts, if  you give them the water in which it had been dipped.

(also known as silkies or selchies)In Ireland called Roane.-are mythological creatures found in Irish, and Scottish folklore. The word derives from earlier Scots selich, (from Old English seolh meaning seal).Selkies are said to live as seals in the sea but shed their skin to become human on land. When a female selkie sheds her skin and a human captures it, she is forced to become his wife. If she were to ever find her skin again, she would return to sea, leaving her husband to pine and die.
Male selkies are very handsome in their human form, and have great seductive powers over human women. They typically seek those who are dissatisfied with their life, such as married women waiting for their fishermen husbands. If a woman wishes to make contact with a selkie male, she has to go to a beach and shed seven tears into the sea.

Tales of mermaids have been around for centuries, and form a large part of seafaring lore, especially round the coastal areas of Britain such as Cornwall, and the Northern Isles of Scotland. Their sighting was thought to be a bad omen, foretelling storms and rough seas. There are numerous folk tales describing their interaction with humans.  Typically Merrows are drawn to the following classes: Mage, Druid, Cleric, Bard, Knight, Healer, Warrior, Artisan, Entertainer, Laymen, Water Mage, Paladin, Hierophant, Warrior Mage, Monk, Seductress, Priest/Priestess.
Merfolk are restricted to wearing Leather armor, forearm and hand armors, robes and circlets, as any sort of heavy chest piece is too bulky for underwater usage.
Weapons: Merfolk can only use any light weaponry, Heavy weapons such as warhammers are too large and bulky for underwater use.

To most mortal races the sea is a dangerous expanse, as risky to cross as any barren desert, if not more-so. To the Merfolk, it is quite simply home, and while in its waters they are in their element. As such, Merfolk are fully capable of both casting spells and engaging in combat while underwater, and suffer no 'man overboard' effects or penalties during Naval combat.

Natural Navigation:
Merfolk have an extremely close relationship with sea and star, moon and tide... able to naturally gauge distance and direction with uncanny ease while in the water, a requirement for a race of peoples which can and often do travel hundreds of miles in a single day's leisurely swim. All Merfolk may choose to begin with Journeyman skill in Navigation if they wish.

Undersea Skillset:
Though merfolk often excel at trades surrounding their natural element, from navigation to angling to harvesting rare materials from the sea-floor, they are exceptionally inept when it comes to trades that would prove impossible underwater. Blacksmithing, glass blowing, horsemanship, carpentry, even cooking and baking... your average Merperson is positively terrible at them all. Merfolk cannot reach expert or master skill in any of the above listed ranked skills.

Those of the Merfolk -must- return to water, fresh or salt, once every two days for the bare minimum of two hours. Though a dip in the bathhouse will suffice in this regard, a land-locked Merperson who finds themselves in captivity is in serious danger of lasting harm. Though Merfolk who have gone more than two days without immersion in water do not necessarily die, they do begin to dry and wither, which will very much resemble rapid aging. This process can be reversed, but only with time and care.

Suggested Sites

Mermaids, Merrows, Mermen:

Celtic Selkies
Monstropedia Selkies

Other Sites
Sea Folk
Sea Monsters From A to Z

Creatures of the waters depths, the Merfolk live a great deal of their lives under the oceans and lakes caress. The Merfolk tend to keep to themselves,rarely leaving the water's embrace to risk the open land, the burdens of dry and grounded living heavy to those used to the weightless and fanciful flight of undersea life. Living among the corals - where no ship usually dares to sail, sea life and fauna, they hold quite open lives with those about them.
The Merfolk are a hearty race, having lived their entire lives dealing with the constant pressure that the undersea can bring, having great natural fortitude and stamina.
 Their flesh has a silken sensation to the touch and often appears in hues ranging from dark blue to light sea foam green when in their merfolk form. This is believed not to be their actual skin color but rather a protective coloration they adopt under water. When in bipedal form, they take on the appearance of a normal human being, with skin tones ranging from pale to a dark rich tan. Their hair color varies from the light blue of the sky to black, depending on the region the merperson was born. The heights of these creatures tend to vary from region to region; however, they never are shorter than 5'0", or taller than 6'4"
Its often said that the Merfolk were given a blessing due to the undying love of one mermaid to a elven or human male that went away on land for extended periods of time, that, while underwater a Merfolk has the bottom half of a fish, fin and all. However, while on land, the Merfolk go through a dramatic change where the fins are replaced by legs for better travel.
The Transformation from "fish' to human is quite remarkable, but the question remains, how exactly do Merfolk reproduce under the waves? Well, prior to the transformation from Sea to Land, the Merfolk keep their humanoid sexual organs, the males often have a sheath that remains hidden for a great part, only coming into view when sexually aroused, and the females is nigh invisible till they're aroused, then the scales around the females vagina change hue, signaling their ready for sexual relations. Often times the coloration ranges from Intense Reds to fiery oranges or other 'loud' colors. As for the males and females anal cavity is a bit more extensive in their mer-form, leading down the tail to where the flipper/fin is and ending there.

The miracle of birth is highly important to the race of merfolk for when they had lived in their icy world, without food, they almost died out since successful pregnancies were few and far between. For each expecting mother, they are to go to the closet temple and thank  their goddess for the miracle and to give offerings of flowers, shells, and etc. When the merbaby arrives, a celebration is held for the child and it is the Head Priest/ess that names the child for the name comes to them from  the goddess herself, if the child is female that is. Male children would receive their name from  the god.

Death is a solemn occasion for the Merfolk, when one of their kin returns to the oceans depths from whence the Great mother spawned them from. Of course, they could always get resurrected and nothing’s prohibiting that.
There are many theories as to what happens when a merfolk dies. Some say that they are a race with no soul and return to the waters as sea foam. This is only half true, for merfolk do have souls, just like any other living creature. If the fallen merfolk has lived for hundreds of years and has let their wishes of moving on to the after-life known, the body is brought to a temple for preparation. The body would be wrapped head to toe in soft layers of white dyed seaweed then decorated with flowers, shells, and something of personal value. Those of the temple then would bring the body to the surface and lay it upon a group of smooth sunning rocks. The area around the body would then be decorated in more sea flowers. All of this would be done when the moon hides behind the clouds, the waters caressed with thick fog so humans might not stumble upon this ritual. After prayers to Gaia to guide the soul to the embrace of the sea foam to live forever among the waves, they would leave the body resting there to be taken by Gaia and transformed in foam.
If the merfolk had only a short time upon this earth, a young merchild or another and they had been unable to tell of their desires to return or live within the sea foam, they would be brought back to the living. The fallen merfolk body would be prepared as any others; however instead of going to the surface for the sea foam ritual, they are taken to a giant oyster shell and placed within. Gaia would be prayed too and worshipped, those family members who brought the fallen to the shell, would beg Gaia for the return of their loved one. If their prayers are answered, the shell would close and remain closed until the breath of life fills the fallen merfolk once again. It could take up to days, weeks, or even months.

In Seamaide:
Much legend and myth surrounds the Merfolk, that strange and fin-tailed race who dwell in the waters of  our lands, but very little actual fact in regards to just who and what they are exists in the public mind. This isn't because these facts aren't available, many Merfolk who have chosen to walk the land are ready enough to explain their past, their culture, and their history... but such tales are rather dull in comparison to the wild yarns the other races tend to weave, and most of them prefer being entertained to being informed.
If there is one thing that Merfolk despise, it is the use of their waters as a dumping ground by the land-locked mortal races. Armed conflict with Merfolk nearly erupted in the early days of Seamaide when sewage from the  village and tavern began finding its way out to sea, where a community of Merfolk happened to be living. After some tense diplomacy and many seemingly sincere apologies, the Merfolk agreed to relocate, but incidents such as this are not at all uncommon, and have lead to many of the less than pleasant myths surrounding them.
One such Myth, and one that very much irritates the Merfolk who hear it, is that Merfolk in general not only hate all land-locked races, but actually eat those whom they lure or drag into the water. The truth is there are next to no recorded incidents of Merfolk attacking the other races, and most of the few such reports were in relation to Merfolk defending their territories from overly aggressive fishing, dolphin poaching, or waste-dumping. "Besides," some Merfolk might muse tongue-in-cheek, " taste terrible." Still, not all the dark tales told by weathered old deckhands in the booze steeped night are false. Much like any other race, even the Merfolk have their share of dirty secrets.
Merfolk society is for the most part a very relaxed affair. Though they do keep 'kingdoms', great castles of coral erected over decades by druids and Heirophants who specialize in the craft, the 'rulers' of these keeps claim no dominance over those around them, expecting to be addressed neither as leader or royalty. These keeps are rarely more grandiose than they need to be, considering the time construction takes, and are erected simply to facilitate the larger Merfolk Families. Merfolk can survive at extreme depths, but rarely make homes of places deep beyond the sun's influence.
Though seeing no better in the dark than the average human, they can navigate darkness with surprising skill using lilts of song in a basic, but still functional form of sonar.
Family units are an interesting subject within the Merfolk’s culture. In a single household, there usually is a single dominant male or female, since there’s little difference between the genders, and several if not dozens of wives or husbands. The Merfolk society is a polygamous one, where a single male can have many wives, or a single female can have many husbands. As such a family of Merfolk can become a community in and of itself, eager to invite those of other families to 'marry' into their household.
The seas and oceans of the world are far too expansive and plentiful for conflicts over space and resources to arise, but there are still threats to their safety which require a certain level of militarism. Many of the Sea's larger creatures are willing to attempt the folly of making food of Merfolk, and though rarely to never successful they can often irreparably damage coral communities in the attempt.
Domesticating sea-creatures is a difficult prospect, but the Merfolk do have very close bonds with certain specimens, dolphins in particular. Though Merfolk make no effort to 'herd' or 'tame' them, a close companionship and co-existence between them is hardly uncommon. Its even said that Dolphins are willing to act as couriers between Merfolk households, carrying news, warnings, sometimes even goods. They also frequently keep smaller sea-creatures as pets, and some families of Merfolk are rumored to have domesticated sharks for their protection.

 Most merrows are expected to not kill others unless it is in self defense or protecting those of the home. Those that do kill for unnecessary reasons are to be casted out and left to defend themselves on their own. Also, they will not use excessive amounts of the ocean life, like killing more fish than needed or taking things naturally found within the waters and selling them for personal gain.

It is forbidden for those of the Merfolk to despoil the waters they hold dear, any doing so is immediately renounced by the race as a whole and thus marked, usually a brand on the forehead or biceps.

Most Merfolk will not willingly go near flames, nor own any magic that deals with the fire sphere. The flames dry out their flesh faster, and most Merfolk that have been near flames feel an immediate need to drench themselves in water to halt the scaling process their skin goes through, which causes an intense pain and often bleeding.

Special Days:
The long weeks of rain during the spring months are all special to the Merfolk, the bringing of their blessed water from the heavens above causing a great celebration, often appearing as an underwater faire. Grand banquets, religious orgies to their Water goddess, tournaments are all commonly seen for these few weeks.