Nephandi

The dumdums who basically run the World of Darkness. A faction of EEEEEVIL Mage: The Ascension, the Nephandi (singular: Nephandus) run the gammut of evil from cackling ass-nekid doom cultists to corporate executives who attend charity banquets while ordering the covert extermination of a low-income neighborhood on the other side of the continent. Many are both.

WoD being as Grimdark as it is, the Nephandi are basically handed a bunch of easy victories in the fluff so they can serve their purpose of making the world terrible, despite the fact that they are kill-on-sight targets for literally every splat, with only some evil ghosts, radioactive werewolves, and aliens as allies, all of which will sell them out at a moment's notice.

Nephandi who become evil deliberately after Awakening are called barabbi, while those born with evil Avatars are called widderslainte.

So You Wanna Be A Nephandus

Why?

Ok fine, whatever. You want to sell your soul to Chaos or whatever. That's cool. Remember that your GM will have to take control and turn your character into an NPC, or Phil Brucato will show up at their house and danse skyclade on their kitchen table until they agree to.

(But seriously, I wouldn't bother with Nephandi PC's. Stupid Evil is only entertaining for so long.)

Anyway, basically you have to jump into an evil vagina gate called a Caul. Then you see your own personal idea of evil. Once you betray your principles and embrace it, your soul is melted down in the oozey jacuzzi and turned into evil soup before being injected back into your body. Congratulations, you can now explore the hell-realms of deformed pseudo-reality called the Qlipphoth, in order to become even more evil and powerful. You fucking doofus.

Qlipphothic Spheres

These probably aren't still canon, because they were pretty unpopular when they were introduced in Revised, but the Nephandi have their own proprietary bag of tricks called Qlipphothic Spheres. They're basically the regular spheres, but evil, geared toward the destruction or corruption of their specific aspect of reality.

Qlipphothic Correspondence is for rending space, severing sympathetic connections, erasing data, and probably making black holes.

Qlipphothic Entropy is like regular Entropy, but eviler. It has an easy time turning the user into a lich and making things fall apart, but kinda sucks at good old-fashioned luck manipulation.

Qlipphothic Forces negates energy, creating cold or stopping kinetic energy in its tracks.

Qlipphothic Life is all about cancer powers and fleshwarping.

Qlipphothic Matter destroys regular, wholesome matter and replaces it with sanity-blasting non-euclidean crimes against physics and chemistry.

Qlipphothic Mind destroys or tarnishes memories and allows the wielder to enter a null-mind state to commune with the evil consciousness of Oblivion or something.

Qlipphothic Prime can unmake or negate other Mages achievements in the form of counterspells and turn Quintessence into unusable evil Quintessence.

Qlipphothic Spirit can kill normal spirits and call up demons, Banes, evil ghosts, and gibbering elder things from the outer darkness.

Qlipphothic Time... I'm gonna be honest, I have no idea. Probably creating time paradoxes and retconning people out of existence? Who knows. Nobody uses these fucking things.

The elusive Tenth Sphere sought by all the various factions in Mage is, according to the Nephandi, the Absolute, or Descent, which basically means the end of the universe. They get their wish in the last of the possible scenarios in the Time of Judgment supplement for the gameline. It's bleak, and not just because it's one of the more poorly-written scenarios in a book that only had one-and-a-half good ones out of the way in the first quarter of the text.

Factions

White Wolf games are nothing if not fractal arrangements of splats, subsplats, and sub-subsplats, arranged in ever finer detail. The Nephandi are no exception.

You have:

The Infernalists, who like to kill puppies for satan. Well ok, that's hardly fair. The Infernalists are actually some of the more organized and pragmatic Nephandi, bartering shrewdly with demons in ways that the Order of Hermes find suspiciously similar to their own. Since they generally meet at black-cloak-and-hood secret conferences around blood-soaked altars in isolated basements, they're not terrible at staying hidden and insinuating themselves into other organizations. It helps that they have literal armies of hapless dupes with demon pacts under their control, which they can use to distract or harry rivals at will.

The Malfeans basically exist to facilitate crossovers with Werewolf: The Apocalypse. They worship the Wyrm, hang out with Black Spiral Dancers and rub shoulders with Pentex executives.

The K'Lasshaa are your Lovecraftian guys. Bearded ax murderers carving the Elder Sign into their victim's foreheads, mad prophets calling down the stars themselves to wreak havoc, etc. You get the idea.

The Baphometites or "Baphies" as they are apparently sometimes called, are evil club kids and hippies who use corrupted tantra and transcendental meditation to control and violate small circles of followers. That is to say that they are date rapists, essentially.

The Heralds of Basilisk are basically a bunch of trolls trying to turn the internet into an evil dragon god through memes. This could either be rad or fucking moronic, depending on the kind of vibe your game is going for.

The Obliviates, also known as the Ex-Futurians, the Eschatonics, or the "Exies", because all Nephandic factions are named with the conventions of highschool cliques, apparently. Most Nephandi are just power-hungry doom wizards hiding their unfettered hedonism behind a thin veneer of cosmic nihilism. In other words, they talk a big game, but actually like being evil too much to really bother with the whole "Armageddon" thing. These are the exceptions. They pursue the power to end reality, be it through wrathful gods, robot uprising, or just a superbug. They're extremely petty, however, and constantly foil each other so the world can end on their terms.

The Ironhands (no cutesy nicknames for these guys) are about the intersection of evil and industry. They work people to death, build WMD's, and dump radioactive waste everywhere. Obviously opposed by heroic, idealistic Technomancers, who see them as a perversion of science's potential, but also alarmingly good infiltrators. Reform-minded Technocrats had best sleep with one eye open. Obvious overlap with the Malfeans goes about as well as you'd expect.

The Mammonites, aka the Cult of the Golden Bull, are exactly what they sound like: evil money wizards. Unlike the Syndicate (who are already pretty amoral to begin with), these guys have not even the slightest desire to use their wealth for anything other than world domination. Also unlike the Syndics, they aren't necessarily technomancers, blending bleeding-edge gadgetry with old-world secret rites.

Los Sangrientos are a pretty obscure faction, focusing on Aztec blood magic twisted through the lens of esoteric Catholicism, keeping the worst traits of both. The adherents style themselves as modern-day Conquistadors. I assume. They only get like one paragraph in one book.

Similarly, the Gatekeepers are the inheritors of an ancient Sumerian astrology cult. They want to stage an alien invasion for their dark masters, which puts them directly at odds with the Void Engineers. Conversely, their similar origins mean that the two organizations often overlap dangerously.