Bestiary of the Bladeseekers #4 - New and Old Merpeople

These cursed forms of the Merfolk are not the most dangerous beings to deal with under the sea, but they come close.

— Tyson MacBogard, Lord Founder.

Carcinated Merfolk

Over the years, my connection to water strider has led me to becoming the Bladeseekers informal ambassador for dealing with seaborn beings, such as Merfolk, more commonly known by the public as mermen and mermaids. Generally speaking these highly intelligent beings have their own civilisations below the waves and do not bother us land dwellers, which is why I don't expect the Bladeseekers to have to deal with them.
Among the Merfolk exists a condition however, which creates monsters roaming in their midst and these monsters are much more likely to cause us trouble.

Appearance

Generally, Merfolk have the appearance of humanoids which have a large tail instead of legs, webbed fingers on their hands and gills instead of lungs. Their skin tends to be in greenish and predominantly blueish colours, which grants them a natural camouflage in water. The beings I am more specifically describing here are different. They start out looking like their reasonable siblings, but at some point in their life a curse manifests itself.

Who are Tyson MacBogard and the Bladeseekers?

Tyson MacBogard, was one of the founding members of a adventurers/mercenary guild in a place outside of the world.
He does not exist within the world of Focis at all, but somehow his writings in the form of the Bestiary of the Bladeseekers have found their way to the world.
More strangely, many of his descriptions match beings that exist on Focis and even more so he sometimes accurately described beings that did not exist in the world of his origin, but do exist on Focis.
The existence of the Bestiary is a mystery still unsolved and the book and its many copies are prized curiosities among many civilisations.

The merfolk I have talked to did not know the cause of the curse. I could speculate if it is magical in nature or a disease, but the point is moot for our purposes. Once the manifestation begins, there is no cure for the Merfolk. It starts with flaky patches of chitinous plates forming beneath the outer layers of the merfolks skin. During this point the afflicted begins noticing an itching feeling and the desire to peel at their own skin.
As the curse progresses, the chitin composite hardens and at the same time the same the tail of the afflicted begins slowly dying off. inside their tail muscles, crablike legs start forming and developing. After a while the skin above the forming exoskeleton starts slowly peeling off, at which point the affliction is noticed at the latest. The afflicted manifest crablike features across their body.
Eventually, the exoskeleton covers the entire body. The tail falls off revealing the new crab tail and legs. Even the face and hands eventually turn more and more crablike, until a monstrous mancrab has replaced the once gentle merfolk.

Habits

A more devious side of this cursed carcinisation is that the process affects the head of the Merfolk last. The victim of the curse is aware of the transformation until the very end. When it is apparent that they are suffering from the affliction, they are cast out of their society.
Then, when the carcinisation of the head begins, the monster is truly born. Due to the difference in head shape, the newly forming exoskeleton is pressing on the brain of the Merfolk, which causes lasting damage to higher functions and induces a shift in personality. The new Crabfolk is less intelligent, but much more aggressive, ravenous (which I suspect also fuels the transformation) and ultimately dangerous to their surroundings.
After the transformation, the Crabfolk becomes a nomadic hunter of the seas, sustaining themselves on instinct and hunting anything even remotely in their own weight class. Occassionally, multiple Crabfolk have been known to form primal tribes in which ruthless cooperation but also deceit is common. Luckily however, this is rare, because despite the fact that the Crabfolk are biologically immortal, the curse is very uncommon and only rarely manifests itself.
Sadly, Crabfolk are also able to produce offspring like normal Merfolk. The curse is however also transmitted to the children, which undergoes its transformation within the womb of its mother and is born fully carcinated. These second generation of Crabfolk are even more feral than their parents, but otherwise are identical in behaviour and abilities.

Whatever is the curse of this carcinisations, it is beyond even divine healing.

— TMB, Lord Founder.

Weaknesses

The carapace of the Crabfolk is both one of their greatest strength and their main weakness. It easily deflects blows from most weapons, but can only give and endure so much power before it snaps, which the Crabfolk can not heal without moulting, which they only do every several years. Their claws also stop them from developing many tools, limiting them to spears and similar weapons they rob from Merfolk.
Additionally, Crabfolk are generally less intelligent than you are, but do not underestimate their ability to use ambushes and traps.

Advice

If you can, immobilise limbs and apply leverage against joints, where the carapace breaks easiest. Unfortunately, almost no weapons can build up enough momentum under water to break the carapace, so only fight them with conventional weapons when on land.
There lances, heavy war hammers (especially ones with a pointy end) can fracture their armor. If you have none of these available, go for weak spots, including the face, the underside of the tail and the joints at which limbs attach to the body.
Good luck and keep the blades honored, Tyson

I do wonder if there is a parallel to the werecreatures which plague us land-dwellers. Maybe someone with more patience and knowledge could find out if the origin of both is the same. Then again, Merfolk don't seem affected by the moon.

— TMB, Lord Founder.