Its very rare, enemy-wise and in weapons. Archibald 🤩 seems to have taken om this question and has reproduced its effect in the Tonitrus, but as much mystery surrounds him as does the dark beasts.
From memory, we see lightning in Paarl, Loran darkbeast, nightmare beasts, and the abhorrent beast(s).
What ties these creatures together?

In Loran, there's a lot of dry sand, which creates static through all the grains rubbing together. When you look around in Loran you see the sparks in the air. That's where the darkbeasts come from
this is the best and most concise answer imo. ive always assumed paarl ate archibald, who was keeping him for his research, and thats why he has the spark hunter badge lol.
Yet Loran itself is a complete mystery. Is the dungeon a remnant of the civilization itself? Is it just the underground? It has the same atmosphere as the nightmare zones (graphics rendering completely changes. It's darker, but clearly more post-processing is used to differentiate itself from the base game. Colors are more saturated, skyboxes and tilesets are different, etc.). So is it a remnant in the form of a nightmare?
They are the ancient civilization of the beast plague. Silverbeasts are their most ancient, and their presence in the Nightmare Frontier is enough proof that that was once Loran. Note that they're only on the outside of Mensis, and when you get inside it was clearly a Pthumerian castle at one point.
i've always interpreted Pthumeru, Loran, Isz, and Hintertomb as dungeons created by different civilizations, in different places, but all kinda doing the same thing (aspiring to ascent, get dat blood, etc.). Yharnam happens to be on/near Pthumeru so was more influenced by it. However past hunters traveled to other places. The fishing village seems more Iszy. Paarl came from somewhere closer to Loran, etc.
However, my head canon from seeing the connection between Bolt and Kin, they could've rejected the Great Ones, and in an evolutionary manner, sought electricity as a defensive mechanism, and so did the church...
;;;j;
Even Paarl?
Why else do you think he drops the Spark Hunter badge? He was either a cohort of Archibald, or Archibald himself (more likely the former since the name)
But what's that got to do with Loran?
Because Loran was afflicted by a beast curse the same as Yharnam was. There's really not more info to glean than what's in game already. It was supposedly a vast, desert-like land from whence these particular beasts came from.
"Loran is a tragic land that was devoured by the sands."
"The tragedy that struck this ailing land of Loran is said to have its roots in the scourge of the beast. Some have made the dreaded extrapolation that Yharnam may be next."
"Archibald was fascinated by the blue sparks that emanate from the hides of the darkbeasts, and dedicated his life to its artificial reproduction, in a style of inquiry that, incidentally, closely followed the methodology of Byrgenwerth."
This tells me that, much like how Byrgenwerth descended into the tombs and found Old Blood, Archibald found the means to reproduce the sparks for his weapon and tools within Loran.
Spark Hunter badge description:
We know from this that Archibald went to the chalice dungeons of Loran. This is where his ideas came from, and hence all his created technology like the Tonitrus.
For more context, the Loran chalice dungeons have a kind of sandstorm always going on, and the enemies have a lot of bolt in them, and if I’m recalling correctly, the final boss of the chalice is a Paarl variant called the Loran Darkbeast.
My thoughts from this and the bolt paper that you can obtain is that it's the dried skin of the Dark beasts. They appear to be bloodless, and mostly skin and bone, so I wouldn't be surprised if they were flayed for the electric properties of their skin
Loran is likely the most ancient civilization in Yharnam. So when you see things like darkbeasts and silverbeasts, you'd notice that they're the plague's different, more brutal form.
Darkbeasts originate from Loran
respectfully are you really asking if the Loran Darkbeasts and Darkbeast Paarl are related? ðŸ˜
Nah bra. Im asking if Paarl is from Loran
Probably. It'd be difficult to actually produce such a being, I imagine. I personally think they excavated him outta there for study.
I always thought of it like, the Darkbeasts actively despise the eldritch Truth/the pursuit of it, and relish in their ignorance.
The Healing Church uses quicksilver to create the Celestial Emissaries and the Brainsuckers, replacing their blood with this volatile metal. Naturally, they are weak to bolt damage, which the Darkbeasts are shrouded in.
At least from what we gather from the Suspicious Beggar, the Darkbeasts are/can be intelligent, which is unusual given beasts' tendency to behave like mere hungry animals and their association with stupidity. This suggests, at least to me, that they choose to act as beasts, possibly out of pure sadism, or a mere disgust with the pretentiousness and hypocrisy of the Hunters and the Healing Church.
As for Paarl, its bones being dumped in a "graveyard" beyond Yahar'gul almost makes me think it was a byproduct of the experiments therein. It reminds me of gashadokuro, the amalgamous, skeletal spirits of numerous starved victims, making me wonder if these greater Darkbeasts represent a collective resentment against the secret society that used them and discarded them... But that's more just a headcanon, lol.
As for Archibald, it'd be no wonder he was despised by the Healing Church, since his fascination with Darkbeasts would run completely against their faith in the arcane. I also like the theory that Archibald is the Suspicious Beggar, given he wears parts of the Harrowed Set worn by Healing Church assassins when disguising themselves among commoners. Perhaps he fully committed to depravity after his peers admonished his research for so long...
I doubt the Healing Church only uses Quicksilver. The Emissaries are a different experiment, using likely Blue Elixirs and certain flowers.
The Beggar was a weird one. Considering the ancient nature of the form, he could've been able to switch at will and become sentient, which would obviously be a very uncommon tactic. Ludwig was a more intelligible variant, as well, as he's not a typical Lycan beast, but a man-horse. Beasts are rarely sentient, he was a clear exception to the rule, because his methods are secretive and less is known about him.
Paarl could've been thrown away, but the broken wall suggests escaping captivity. Archibald may have met Paarl in the Chalice Dungeons (not possible to see in his human form because he's clearly ancient) and brought him to Yahar'Gul for experimentation.
I don't hate your theory on the identity of the Beggar, but imo I prefer him either being a very secretive ex-member of the church and/or him being Irreverent Izzy, as the one who can transform into a Darkbeast like a werewolf, assuming he can be human again, could easily invent other useful workshop tools.
I think it's obvious they used more than quicksilver, lol, but it's certainly a key component, given these enemies literally bleed silver when struck, and frequently drop QS bullets instead of blood vials. The Research Hall Patients do not bleed silver, though, suggesting QS was implemented later and aided in their perfection as Celestial Emissaries. The Brainsuckers had some sort of gastropod grafted to the inside of their cranium, and it bears an unusual resemblance to the Kos Parasite. Ebrietas bleeds both silver and red blood.
I always figured Izzy was the Beast Claw Hunter found in Loran, tbh. Besides, Archibald was specifically intrigued by the blue sparks of Darkbeasts, and the Beast Claw doesn't retain these. I think if Archibald were to become a beast, it would probably be an Abhorrent Beast instead of the form borrowed through Beast's Embrace, which enhances the Beast Claw created by Izzy.
So what happened is he drank a blueberry redbull at 3am
The worst kind... I can see why the anger.
There's a couple different lines of thought. As the top comment has pointed out in Loran certain rooms will have lightning arcing about the sand. I wouldn't really attribute this to static electricity due to the sand being dry though, it's probably some sort of magic. Another idea is that certain beasts have the ability to wield fire with said fire potentially originating from blood. We see things like this when in regards to the beast possessed souls and Loran clerics who are not beasts but are partially transformed(Lady Maria and Pthumerians wield blood and fire as well). So considering beasts connection to fire some think other beasts ability to wield lightning might have to do with their fire ability evolving or mutating and becoming more powerful. Another idea might posit it being connected to blood gems. Cut content shows Archibald would ask the player for blood gems and the bolt hunter badge has a sort of gem at its center. The final idea would be connected to the cur Great One beast boss. This boss's full name was Fauna the silverbeasts and she was connected to Loran(and the Moon Presence). So the Loran Silverbeasts and Darkbeasts might derive their power from her as she was Great One beast from Loran who could wield lightning. The only other entity that's connected to lightning is Kos or the Orphan as the fishing priests and the he orphan can also wield lightning magic. Another interesting theory is that the darkbeasts undead nature and connection to lightning could be inspired by Frankenstein and the pauedo scientific belief that electricity could reanimate the dead. Anyway all these theories are equally as viable so just pick the one you like. There might be more but those are the ones I know.
having to sift through dozens of "joke" responses is the worst thing about reddit..... none of you are that funny lol
Eh, I enjoy them.
I frankly disagree with the static electricity answer, if only because it doesn't explain how to can raise a frickin' skeleton from the dead( this thing is FUR and BONE,for fuck's sake! It's got no muscles or nervous system!). But also because of another thing...
They can command wind as well.
Let me explain.
There is a clear set of evolutionary lines to work with.
First, there's normal beasts as we know them. Black fur, specifically ( will return to this point)Then, there are beasts like the Suspicious Beggar; " Abhorrent" beasts, which are smaller than Paarl, but alive, have humanoid-looking faces, and can use lightning and wind.
This is clearer in them than the Paarl-like Darkbeasts, because some of their attacks purely use wind( like that "push" they do, or their clawing at you) , but if you look closely at their larger, skeletal counterparts, you'll notice that current of wind is responsible for "holding them up", so to speak, as when you knock them down and both the wind and the current disappear, they seem to struggle under their own weight.
Now, the most concerning ability the Abhorrents have, particularly in the case of the Suspicious Beggar, is apparently the ability to take human form.
They do not simply have human faces; they are lucid. They can think. Speak. Even in beast form. And the Beggar does all this even though he clearly still is ruled by his hunger for flesh. He is a methodical predator; patient. Efficient....
But wait; there's more.
Remember the point I made about black fur?
Well, let's return to it for a moment.
If you've gone around Central Yharnam a few times, you'll have noticed certain extremely tall beastfolk,holding torches and large weapons. Tall, lean, and with reddish-brown fur...
And horns.
They don't fear fire as much as the next beast, evidently, if we go by the torches they usually hold in one hand. But they're clearly further along the process of transforming than others....
But what about those horns, though?
Well, if you go down to Loran, you'll find something similar happening.
The clerics with staffs are also beastlike, and also have horns. And most importantly, they use fire sorceries...
But why stop there?
Both of these are clearly relatives to a third, infamous cousin;
The Beast-Possessed Soul, one of whom you find at the bottom of the church tower.
Y'know, the one us dungeon diggers have fun luring to other beasts just to watch him cook them all with, you guessed it, fire magic. Which it somehow knows how to use. Specifically, in the form of pyromancy.
No matter which way we put it, there's a clear difference between these folk and Darkbeasts, yeah?
What am I getting at with all this?
"secret symbol left by Caryll, runesmith of Byrgenwerth. A transcription of the roar of a labyrinth beast, the bearer of the "Beast" rune has accentuated transformation effects.
"Beast" is one of the early Caryll Runes. as well as one of the first to be deemed forbidden. The discovery of blood entailed the discovery of undesirable beasts."
Beast Rune.
I've always found this description curious, because Runes are supposed to be the transcribed words of....Well, the Great Ones. This is why they hold the divine power necessary to buff you as they do...
So, how did a beast of all things speak this one?
My theory is only the shape of a theory, but it is as follows;
Loran went further than anyone else when it came to beasthood.
Beasthood is a path that, if you go far enough, has as many secret truths as Insight. Hence the Rune.
These truths are related to the " magic" both the Darkbeasts and Beast-Possessed Souls seem to use.
I'll stop here, 'cause this got a bit long.
Where there's prey, there's predators.
I always interpreted the Plague of Beasts as a sort-of natural counter to the Great Ones. Their eldritch knowledge is so profound and all-encompassing, their presence so oppressive, that nature itself reacted to it. The evolution of beasts thus led into a direction that would give them an edge on Kin and Great Ones. Fangs and Claws to slash and pierce (thrust damage), bolt to strike and disrupt.
Can't overwhelm you with otherworldly knowledge if you're too dumb to understand it. Or your strength of will is great enough to simply ignore it and stick to your own bloodlust and savagery.
There's also a theme of evolution in the game. Different factions tried to become different things. Unintended outcomes were achieved. Experiments failed. Lots of weirdness. It stands to reason that in the world of Bloodborne the potential for change in humanity is vast, yet thanks to the Old Blood the path of beasthood is the most prominent one. Perhaps even a "natural" evolution sped up, given that it is so consistent and some items allude to the idea that the beastly tendency can be awoken without ever actually consuming blood.
Man fuck this thing, i just tried to fight it for the first time and it annihilated me.
I had the same questions like you, I find it really interesting and intriguing
I vaguely recall some lore speculation that the Darkbeasts were an artificial creation the residents of Loran made to try and kill the Great Ones, since Lightning is effective against the Kin
I think it's just power. Raw power. The beasts that are on fire have their blood igniting as indicative of the potency of their blood, the self destroying nature of their strength and, in most cases, the impossibility of actually controlling this eldritch power that eats you up from the inside.
Lighting could be a more refined version of that. Or indicate that, though the blood dried up and it can no longer ignite, its strength is imbued in the dessicated flesh and undying bones of old/ancient beasts.
Friction
Haven’t you heard of Sonic?