The Darkness is a mindless, all-consuming force literally made of everything evil in the world. It can grow in every single place where something horrible or tragic happened (which considering we are talking about the World of Darkness might as well mean nearly everywhere) and corrupt any living being who stays for too long in the places it has tainted. Those who suffer its Taint (known as Darkened) see their mind and body gradually warped as they sink into depravity, until they eventually turn into Darkspawns, mindless monsters who instinctively look for Tainted places and try to drag more people into them. The only way to cure a Darkened before he loses all his Integrity is by convincing him to do something selfless, such as a big sacrifice or saving someone's life, which considering they are slowly losing morality is improbable at best. And even if you somehow do manage to cure them, all the dark powers that had been warping their bodies are instantly removed, resulting in horrible injuries that are likely to kill them on the spot.
Those whose bodies have not shifted enough to become Darkspawns end up becoming Mnemosyne, who do retain their body and intellect, but are still Tainted on the inside to the point they no longer qualify as humans. The fact they still are human-looking and intelligent mean they can not only lead the mindless Darkspawns in a coherent way, but also stay on Earth, where they frequently found Cults to turn even more people into Darkened by teaching them how to meditate in Tainted areas. Oh, and they do have their own kind of powers, the Caligines, which basically amount to Darkness magic they get by practicing ritualistic sacrifices. And they can teach them to Darkspawns.
And then you have the Cataphractoi, ghosts of people who died having crossed the Despair Event Horizon to the point they came back as creatures of the Darkness. In addition to combining the abilities of both the Darkspawns and the Mnemosyne, they also have a warped counterpart to the Princesses' ability to transform, allowing them to turn into nightmarish aberrations with more power than their humanoid form. Oh, and they know how they form, so you can fully expect them to find more people to torture and break just so they will become new Cataphractoi.
Some of the sample Dark Beings offered by the book are quite nightmarish of their own. Many sound more like creatures from Silent Hill rather than a Magical Girl game:
Cradlesnatchers are fat, grotesque, boogeyman-like creatures born from the servants of organized crime and politicians. They specialize in lurking inside bedrooms at night so they can kidnap children to take them God knows where, never to be seen again.
Heartleeches are born from people who have betrayed everything they love and given up everything in the name of their own hubris. This results in their body being left to rot behind, while their tongue squirms free, sprouts centipede-like legs and crawls around to find people and whisper into their ears, filling their dreams with Darkness. And there are rumors they can also crawl down the throat of sleepers and whisper from their guts.
Duskhounds are disturbing Mix And Match Critters of humans and canines which no one know for sure whether they started out as the former or the latter. They don't need to eat and can't taste food, and as such hunt for the sole sake of inflicting pain and suffering. Fighting like wolves, they usually make heavy use of Combat Pragmatism and attack in number, using one of them to distract the target while the other deliver quick attacks and fall back before relatation can be done. And they will use that kind of tactic even against obviously inferior foes, usually for the sake of cruelty.
Lickermen look like shriveled, starved corpses with no genitals, leathery skin, long limbs and a blackened tongue as long as a human's arm, the rest of their mouth being otherwise sewn up with stitches of their own bones. Mnemosyne and Cataphractoi typically like to use them as stalking hounds, but when they are on their own, they like to target isolated prey, with a preference for children and people with high Integrity. And they never damage the bodies, because they feed off the destruction of innocents.
Hundred-Handed are Darkspawns whose exact origin is unknown, though the most common theory is that they form from Tainted bodies. Only barely sentient creatures who lack even animalistic intelligence, they look like gigantic, bulging, cancerous lumps of flesh with two thick legs and several mismatched arms, which constantly reach inside to rip out the things' own organs and throw them as projectiles at the opponent.
Some Umbrae have drawbacks pretty terrifying of their own in how they make you Blessed with Suck:
Faceless in the Crowd prevents people from noticing or remembering you, effectively making you great at spying and sneaking around and giving you an easy way to escape pursuers. Pretty neat, right? Except the reason this happens is because the Darkness is taking away your identity, and everyone's memory of you with it. Childhood friends will forget your name, people you have known for a long time will have trouble recognizing your face, and neighbors will be startled to even notice you in your own house, even if you have lived here for years. Have fun being literally a nobody.
Dark Dream gives you the ability to see visions from the future in your dream... in the form of disturbing nightmares preventing you to have a good sleep. That is, if you are lucky; sometimes, they will also come at the cost of becoming permanently blind.
Corruption of the Blood gives you the ability to make anyone you touch sick... with absolutely no control over it. People will always get sick when you touch them, whether you want it or not. Forget Can't Have Sex, Ever, you no longer can hope to kiss, or even shake hands, without grossing people out and harming them.
Corruption of Flesh allows you to instantly turn anyone you kill into Darkspawn servants for yourself at the cost of one of your dots of Shadows. Nothing bad for you so far... except that once you have exhausted your dots of Shadows, you must use your dots of Intelligence, and then your dots of Stamina, meaning you progressively lose your sentience, and then your resilience. Most Darkened with this Umbrae rarely last for very long, because they tend to rot away as their stamina is consumed.
Caligines, while mostly lacking the Blessed with Suck drawbacks of Umbrae, are pretty horrifying of their own:
Crafted With Love and Care allows its user to trap living victims inside animated dolls of themselves, which he then has complete control over. Essentially, it allows a creature of the Darkness to turn people into its Creepy Doll servants, while still keeping them alive. Worse, the effect is indefinite; so if you don't have access to magic nothing you can do can free the victim.
World-Corroding Entropic Touch basically is a Touch of Death turned up to eleven, allowing the user to destroy everything he touches, including flesh (which translates into 1 Aggravated damage per turn of contact). This is pretty terrifying already, but worse again is the Power Incontinence that comes with it: it also affects the user's hair and clothes (leaving him naked and bald whenever he uses it), and even his tears (which boil on his face as a result). The powers usually lasts only one scene, but it's possible to make it permanent, in which case it can never be shut down, period. Darkspawns and Darkened stupid enough to do this often end up creating near-bottomless pits in the Dark World as they fall into dormancy and the Caligo keeps working, corroding the ground where they are standing and sending them in an endless fall...
Flesh of My Flesh allows the user to heal himself... without Shapeshifter Baggage, meaning the user has to find the raw organic material somewhere else. Multiple ways to achieve that exist, from just eating a lot of flesh to sewing it directly to your body
Some Twilight Charms are just as disturbing:
One of the most basic Tempesta Charms, Corrosive Grasp, allows its user to generate acid from her hands. Among the possible uses suggested for it is to scar a prisoner with the acid as a meant to intimidate him during interrogation. And this is an ability accessible to Princesses, not the Darkness.
Most Specchio Charms actually are pretty funny and entertaining compared to Tempesta and Lacrima Charms... until you get to Enduring Beauty, a Charm whose purpose is to peel beauty from someone's face to make it into a magic gem, disfiguring the victim in the process.
Speaking of Specchio, consider the fact that some of their texts denotes that they sometimes help on Amanojaku hunts. You know, the body snatchers that kidnap real people and leave them stranded in the Dreamlands? Not to mention the fact that Princesses can remain in the Dreamlands for a time before choosing to reincarnate. Now let's bring up a charm known as Ivory Gate and a Specchio Upgrade "Dream of Me", which lets the Princess enter the persons dreams without their consent. If a dead Princess of Mirrors wanted to return to reality, what's to stop her from body snatching some poor person to resume her True Heir duties?
One Sample Dethroned proposed by the book is the Witch in the Wood, a Princess who was cast away from her village for her powers and ended up eating the two children she was trying to raise. She now routinely repeats these events by luring Darkspawns and small children to her cabin, where she tries to take care of them like a mother would, but always ends up eating them "for their own sake".
The Cult of Broken Dreams are Combat Sadomasochists who preach suffering is the one noble thing in human life, teach their members to torture themselves until they become Too Kinky to Torture, and then send them torture more people.
The Pleasure Parlour basically is the Darkness' equivalent of a drug trade: they offer to help you with things outside of morality for cutthroat prices, then try the best they can to get you hooked to them so you'll keep coming back for more, getting you progressively closer to turn into Darkspawns.
The one thing possibly scarier than the Darkness itself is the place where it comes from, the Dark World. It's described as exactly what the trope it's named after would imply: a warped, corrupt, devastated version of the real world, where the streets are ruined, the sun is a faint red dwarf, the moon is a light-devouring void in the night's sky, the air hangs still and chill, and every living thing rots. Even Darkspawns usually freeze in a dormant state here, unless they stick to places connected to Tainted Areas in the real world. Mortals who somehow end up there are likely to get killed in a matter of seconds, for Everything Is Trying to Kill You, and while Princesses can at least defend themselves, they are likely to die quickly as well, since their mere presence in Transformed state attracts Creatures of Darkness. The only things who can freely walk around are the Dethroned, and they are essentially Walking Wastelands, constantly warping the landscape with their abilities.
One thing that's even freakier is that in Mage: The Awakening terms, the Dark World is a Lower Depth. In other words, something like the Inferno where Infernal Demons spring from or the Tutor that the Seers use to make people into empty shells. All Lower Depths are lacking in one thing that would complete their existence, and the thing the Dark World lacks? Hope.
Not even the Twilight Courts, the Grey in the White-and-Grey Morality of the setting, are exempt from this.
The Court and Queen of Tears live in the Dark World (theorized to be the Dark World's Moon) constantly sucking the world of hope to keep up their Wards that keep the Darkness out. Their entire Philosophy is based around Always Save the Girl and world domination, and they're willing to damn the world for their loved ones (Alhambra and its people itself in the Queen of Tears case). They also have Protectorates, which are basically Embassies based on Tear's Dominion over EARTH and further capitalize on Wisp taxing, a few examples being making normal humans into Alhambra's foot soldiers, taking Vampire's havens and ghouls for their own and even acting as an official of the Everflowing One herself and be able to promote and demote anyone with a job! If you happen to be harmed as a part of their goals, they'll write you off as a "necessary sacrifice" and nothing more. The worst thing? The Queen of Tears is basically confirmed to be at Belief 1. Just a single realization that she could've moved elsewhere before she becomes a Queen-tiered Dethroned.
The Court and Queen of Storms also live in the Dark World, but unlike the Court and Queen of Tears, they live on as a living natural disaster that scorches, torches, incinerates and utterly destroys every part of the Dark World that she touches. She is utterly fueled on hatred and her philosophies revolve around the destruction of the Earth if the Darkness were to take it and that all Darkness must die. Even if it's your beloved sister who has been Darkened on no account of her own, and if you so much as show mercy the Princess loses access to Tempesta which can only be regained by filling all of her health boxes with damage. There's more than a few things stating that the Queen of Storms isn't even fundamentally human anymore, that her Invocation is all she is. Even worse, she can create Sworn if anyone believes in her ideals enough, and all of her Princesses and Sworn are more than willing to go out in a blaze of glory against the Darkness. Finally, all of their charms cause Resistant damage, which doesn't heal by ANY means except natural ones. It's wholly possible for a Princess or Sworn of Storms to die from this, and if they do, they'll be subsumed into the Queen of Storms and become another part of her to forever fight the Darkness. The Princesses of Storms believe that if she gets enough souls, she'll be strong enough to purge the darkness from the world... with the implication from Diamonds that it'll destroy the world in the process.
The Court and Queen of Mirrors are enigmatic and may be Wide Eyed Idealists, but no less scary or creepy. For one, the Queen of Mirrors is publically a Hidden Agenda Villain. Anything on her or her plans are unknown save that she was a child queen who fled the Kingdoms in the Fall and wants to find the True Heir. Her Invocation causes madness, especially of the Narcissism variety that WILL eventually mess up any Specchio user. It's unknown how she keeps her Queenly status when she doesn't publically have a Court. If anything, her Nobles are also just as scary. They're all told by the Queen of Mirrors herself that they're the True Heir, but because of Mirror's Philosophies, they all despise each other because there can only be one True Heir. Their level of Narcissism and expectations of restoring the Kingdom and ruling it also tends to lead to VERY bad conclusions. For various examples, their Narcissism leads them to work on their own and be extremely noticable for what they are, which leads more often than not to them being found by and killed by Creatures of Darkness. If any of them fail in their expectations and lose Belief, they're more likely than not to go MORE crazy. Their grandiose level of expectations that they bear and their powerful charms which can be summed up as self-buffing tend to lead people to trust them unconditionally, as an example being a single Heir defending a city would leave it all to herself and make the people relax because she will take care of it. If an army were to attack the town, everyone would more than likely be dead. The most terrifying prospect of the Heirs though? Most of them tend to be CHILDREN. No child should have to face anything the Princesses of Mirrors typically fall to! Even the corebook developers split on how bad they can be. On one hand, they can simply be useless jerkasses who refuse to compromise their beliefs. On the other, they can be complete narcissists who demand to control everything and will sabotage other princesses, all of their efforts merely being a long road that always ends in either their deaths or Dethronement.
You thought the Court of Storms wasn't scary enough already? Meet the Goalenu. Ephemeral creatures believed to be incarnations of Tempesta itself, these things are the Seraphic General's lieutenants, essentially implied to have been created by merging the souls of several of her champions together. In their natural state, they are more or less powerful ghosts infused with Tempesta energy and powers, but they are capable of either possessing people (injuring both the host and themselves in the process) or crafting themselves an artificial body called "vessel", which they create combining two essential components... clay and flesh. Including a heart that has to come directly from a human chest. Too much clay to the mix results in them looking more or less like oversized porcelain dolls, and each damage they take reveals a little bit more that they aren't human. Oh, and they can acquire the skills of the people they steal flesh from... meaning Goalenu will frequently go after experts in various fields so they can harvest their organs.
The Dreamlands might seem like a nice place to be in at first... until you stick around for too long and the remnants of its Lotus-Eater Machine start manifesting, gradually modifying your memory and appearance to assimilate you as part of it. You will suddenly start remembering living here from birth, while it becomes harder and harder to remember your life in the real world. Unless you wake up soon enough, and stay away from the Dreamlands for some time before your next visit, you will end up trapped here without even knowing it, because you will think you really are just another Dreamlander, and only another Princess will be able to get you out of here. And the process happens faster if you don't spend most of your time transformed, meaning Sworns, Beacons and mortals who somehow ended up here are even more likely to fall victim of this.
And to make things worse, the Wardens who were in charge of maintaining the illusion still exist, albeit in smaller number and hidden in the deepest regions; Should you meet them, they are capable of changing your memory even further and trick you into living fake adventures, all so they can convince you to stay even longer here. And the more the Dreamlands have already affected you, the stronger their influence on your mind will be.
There are also Amanojaku, essentially underground criminal Dreamlanders who use profane magic to get to the real world through stealing bodies from Mortals. The method they use for that is disturbingly reminiscent of Freddy Krueger, as they use "doors" to get inside a human's dream, then twist said dream into a nightmare where they act as monsters chasing the human's soul. Once they get their hands on said soul, they throw it to the Dreamlands and take its place, living the unfortunate victim's life while her real self gets slowly assimilated and turned into a Dreamlander as described above. Oh, and they have devices called Gates of Polished Horns, which allow them to do that on a larger scale, stealing bodies not from one mortal, but all his family and friends.
Oh, and let's not forget that the Darkness still exists in the Dreamlands, with Tainted Areas and everything. A particularly sinister story is described in the book about a Nakama who found a cursed area almost entirely covered by the Darkness, populated by crazy sharp-fanged folks who ritually consumed victims on altars in the name of what they called the "Red Word". Only one of them made it out alive, while the others were devoured, which somehow resulted in them dying in the real world.
Oh, and that little "Red Word" Cult? That's actually a thing in Mage: The Awakening, specifically Boston Unveiled. They're a delightful little cult in service to the Prince of 100,000 Leaves-essentially, an Alternate History so horrifying that reality itself spat it into the Abyss, where it became sentient, and angry. Sweet dreams.
