Mermaids are hypersocial carnivores. They feed exclusively on land-dwelling mammals, including humans and demihumans.
AC 6 , HD 6 (27hp), Att 2 x grapple (1d3), bite (1d4/3d6), THACO 14 [+5], MV 360' (120') swimming, 30' (10') crawling, SV D12 W13 P14 B15 S16 (3), ML 5, AL (CG? Chaotic? Neutral? You figure it out), XP 275, NA 0 (2d8), TT 1 in 6 chance of 1d6 pieces of jewelry.
- Automatically attack if there is (landfolk) blood in the water.
- Damage from grappling attacks becomes ongoing until target breaks free.
- Once both hands have grappled bite damage is applied automatically. If they try to bite without grappling first, a hit only deals 1d4 damage.
- Many mermaids are younger specimens with 4 or 5 HD.
- Parties encountering mermaids for the first time who approach in a friendly manner have a +4 on the reaction roll. Once they make friends or enemies of the mermaids, further encounters will react accordingly.
- Retreats on 3/4 hp.
- If not using other rules for underwater combat, +4 to attack and defense while fighting land-dwelling creatures in the water.
Landfolk and mermaids are mutually delicious; mermaid sushi is a decadent delicacy among the wicked; their skin is fragrant, their kisses are sweet. Land dwellers are every bit as tasty to them. Conversely, they have little interest in eating other sea creatures and never cannibalize one another.
Mermaids have characteristics which in humans would be associated with ADHD: They are restless, playful, easily bored, struggle to focus on tasks that do not interest them, and show hyperfocus on things that do. This leads many landfolk to dismiss them as stupid, but they are highly intelligent, and specialized for their ecological niche.
Their hypersociality is both a means of organizing their community and part of their hunting strategy. Where a human might have a circle of 250 or so friends and associates, a mermaid can easily keep track of thousands. It is reasonable to assume that every mermaid you encounter knows every other mermaid, as well as numerous landfolk and denizens of the sea. All mermaids speak numerous languages, including the common tongue, their own and those of whales and dolphins.
They are extremely friendly, even flirtatious if such advances seem welcome. This is part of their strategy for luring prey into the water, but it is important to note that this is not an act on the part of the mermaid - they are genuinely gregarious and love to make friends, even if these friendships are sometimes all too brief.
A swimmer cavorting with mermaids will find them eager to play and cuddle, kissing with giddy eagerness, perhaps a nibble here, a slight nip, their teeth surprisingly sharp - oops, she's drawn blood, nothing serious, just a little ribbon of red hanging in the water.
As soon as they taste blood in the water, every mermaid nearby will draw back her lips to reveal sharp, sharp teeth, their eyes will dilate, taking on a giddy look, and as one they will fall on their prey and strip it to the bone in minutes.
If they liked the swimmer, they'll feel bad about it afterwards, though the mermaid temperament is not given to dwelling long on such morose things.
If they disliked the swimmer, they will show no remorse. Just as mermaids can easily keep track of their many friends, they never forget their enemies. They nurse grudges and kill those who make enemies of them gleefully and without mercy.
Lacking the elongated jaws of most predators, the mermaid attacks by grappling with both hands, her powerful grip dealing 1d3/1d3 damage. This damage is repeated every round after an attack hits unless the target breaks free, and once both hands are grasping the target she will bite for 3d6 automatic damage per round, her saliva containing enzymes that break down the flesh of land-dwelling organisms - her bite will deal only 2d6 damage to sea creatures.
Mermaids are not brave and have no interest in a fair fight; they rely on surprise, numbers, and viciousness to kill their prey quickly. A mermaid will retreat after losing a quarter of her hit points. As a result they will often seek help in taking on powerful foes they bear a grudge against.
Profitable relationships can be had between mermaids on the basis of common enemies or the regular need to dispose of fresh, tasty corpses. Animal meat will placate them but does not excite the way human flesh does.
One can frolic with mermaids in some semblance of safety by ensuring they are well fed beforehand, checking carefully for open wounds, being firm about not letting them bite, learning to recognize the loopy look of a hungry mermaid, and if all else fails, a firm bop on the nose can disrupt their feeding state. Though this risks annoying the mermaid, they will usually forgive nonlethal self-defense in the same spirit as they expect their friends to forgive the occasional devouring attempt.
Sidebar: (Since someone is going to ask) Can you fuck a mermaid?
There's a big difference between can and should.
Here's the thing: They're probably DTF, but mermaids are not sexual; they engage with the act on an affectionate and sensual level, and the reason it's sensual to her is that you taste nice. If you do this thing she will eat you.
In the event that this is your fetish I only beg that you make sure the rest of your table share your enthusiasm before indulging it.
They are excellent messengers, able to relay messages not only among their own kind but also through the intercession of whales and their long-distance songs; they know useful contacts for PCs both on land and beneath the waves. They are in theory skilled translators but lack the focus to translate long texts.
They are amoral in the sense that they do not spend time contemplating the suffering of the world in the abstract, but they are highly sympathetic and can easily be won over by a sob story.
To the naive landlubber they may seem to be just piscean dream-girls, offering a love uncomplicated by terrene concerns; to the old salt they are evil spirits, cunning, deceitful sirens luring good men to their deaths, and to merely look upon or speak with them is ill-omened.
The truth is that mermaids are sincere, friendly, and kind to a fault. But they are not human. They do not think like humans, and those who traffic with mermaids do well to remember that they are ethically, mentally, and physically alien.
Mermaids live until they are eaten, or until they lose their excitement and love of life, and ennui overtakes them, at which point they sink down to the bottom of the ocean, lay their eggs and die. There the hulking, dour, benthic mer-men bury the mermaid in a cairn of coral with sombre ceremonies, fertilize the eggs externally, and raise the hatchlings.
The males are taught the solemn, serious, and stoical ways of the mer-men, and dwell with them amid ruins on the deep ocean floor, while the females, as soon as they are strong enough to swim, surge upward eager to explore and frolic in the sun and escape the dullness of the mer-men and their lightless world.
Sidebar: But what if I don't want to frolic?
The occasional nonconforming gothy mermaid remains in the deeps, while once in a while an ebullient mer-man swims up with his sisters to dwell with them in the shallows. These variations, rare on account of the extreme sexual dimorphism of the species, are fully accepted by the group they join when they do occur - merfolk gender roles are reproduced by instinct and, as a result, not socially enforced.
Upon reaching the surface they are greeted by other mermaids, who teach them to hunt and make friends and swim and all the other skills a growing mermaid needs. The only familial relationship they know is "sister", and they are all sisters. Anyone who reminds them of a vulnerable young mermaid is likely to be regarded as a sister too (regardless of gender) and they will become very protective. They are patient swimming instructors, even for those without tails.
Other sea creatures respect mermaids, either for their sociability and usefulness as messengers, or (in the case of the Sahaugin) for their hunting prowess and ferocious appetites.
Mermaids are mythological creatures, formed of the tales, desires, and fears of lonely sailors, but it is their practice of mutual solidarity, ability to form strong out-group bonds, and terrifyingly effective (if partly unconscious) hunting strategy that has allowed them to thrive and multiply.
Reclining Mermaid by Kris Guidio