In Mahou Sensei Negima!, love spells are forbidden because they reach into someone and change their private self. Hypocritically, this does not extend to Laser-Guided Amnesia in order to protect the Masquerade. In addition, Negi knows a forbidden spell that would result in killing a demon instead of binding or banishing it. What the details or consequences of such a spell would be are not shown, as he chooses not to use it, but... it is ademon, which is just another race in the Magic World..
Later on, Negi learns a technique called Magia Erebea developed by Evangeline, which depends on negative emotions such as hate, rage, fear, or sorrow, and takes a major toll on the user's body and soul. According to a demon Negi fights later, it works by the magician taking an offensive spell into himself for empowerment - basically, swallowing your own lightning spell to become a human thundergod. Considering that 'Erebea' looks a lot like 'Erebus', alternately the son of Chaos or part of the underworld... yeah.
The author explains the word's roots in a lexicon entry and directly references Erebos, so it is quite literally "Magic of Darkness". However, both Negi and Eva elaborates on what exactly Magia Erebea is: "the power to take in good and evil, strength and weakness, and accept everything, exactly as it is."
Hottip'd for uber length
Because of the way that the supplemental materials explains it, Erebos is made clear to be a force of "darkness" in the sense of "the chaos in the origin of the universe, before creation, when all was chaos", not in the sense of "opposing light". (It even goes on to explain how light was created out of the darkness, that light opposes darkness, but darkness does not oppose light.) The Dark Magic Negi uses is one whose origin appears to be something akin to a Freudian "ID" (requiring a Battle in the Center of the Mind to use, as well), and contains all his "good" and "evil" impulses, equally. Since it isn't evil in exclusion of good, its source is the (admittedly, negative) emotions and magic power of the user, its costs are purely to the user (and other techniques that drain plenty of your power are just as dangerous in much the same way,) and its effects are just more powerful destruction than the other "good" ways to blow stuff up, the Dark Magic Negi uses qualifies more as a Yin Yang Bomb than Black Magic, and Dark Magic is Dark Is Not Evil in this case.
Oh, and if the person using it is completely consumed by rage, they turn into THIS.
Which is eerily similar to the Lifemaker's appearance here and here.
And it turns out that the technique wasn't designed for normal humans, so using it enough will eventually turn you into a demon, so it is likely a little ten year old boy will turn into a demon for using this. He doesn't seem to mind so much though.
Curiously, in Slayers, Black Magic is in fact fueled by the dark energy radiated by the various demonic Mazoku Lords. However, humans can tap into this without ill effects, since this is a divine function to maintain the Balance Between Good and Evil.
The only rule is the mazoku themselves are immune to any spell from them or a mazoku subservient to them. Thus Shabranigdo, the main Dark Lord, can just choose to not be affected by any Black Magic. This is most dramatically demonstrated in the last novel, when a shard of Shabranigdo chooses not to be unaffected by the dragon slave, and is killed that way. Using against a Mazoku Lord a spell summoning the power of him-/her-/itself (or power of servants they created), as Lina put it,
...is like saying: 'Hey, you! Can you help me kill you?'
There's a second rule about Black Magic for Mazoku. They can't cast Black Magic of other Mazoku. Meaning that even as strong as Hellmaster and Dynast are, they can't cast a Dragon Slave or any spells of other Lords without killing themselves in the process.
Further, there's a distinction made within Black Magic between Curses and Destructive spells. Curses are almost uniformly seen as evil (though the really twisted stuff is exclusively used by demons). Destructive spells, on the other hand, are value-neutral, given that a large number of Shamanic (elemental) spells can accomplish the same result (Fireball, for instance, uses fire spirit, not Mazoku).
The alchemy of the 2003 anime adaptation eventually turns out to be fueled by the death and suffering of those in Real Life Earth, and is implied to be behind the world wars.
Arguably, Hiei's Dragon of the Darkness Flame technique in YuYu Hakusho. It falls under the category of hellfire, as it comes from the demon underworld. However, it only requires a sacrifice when the user is not strong enough to control it ("I suppose just my right arm will do,") and is used by Hiei to fight various enemies who have less-than-honorable intentions.
The Yu-Gi-Oh! franchise has the Shadow games, which utilize dark magic and utilize rules for each game.
More specifically, there's the Dark Magician (actually called the Black Magician in Japan), although it's unclear why the magic would be classified as evil. The Dark Magician was created through a noble cause, he only uses his own life energy, and his purpose is to defend the Pharoah. The card is also used by Yugi, the main protagonist, who isn't evil.
The manga brings up a second Black Magic user, Romania.
In the Fairy Tail world, the title "Black Mage" Zeref is taken very seriously.
Film - Animated
Rothbar and following Big Bads in the The Swan Princess movies, all clamour for the power of 'The Forbidden Arts', the magic of Change, Creation and of course, Destruction. The powers themselves tend to take the form of a glowing crystal ball that, if destroyed, takes the powers away from anyone using them - explosively
Unless you ask a follower of the Grey Jedi philosophy, which says that neither side of the force is actually 'good' or 'evil', what matters is what you do with it. This is widely considered heresy by Jedi and Sith alike.
This is taken to new heights in the Expanded Universe, where Sith Alchemy is an actual, defined practice that ranges anywhere from making indestructible swords to turning preexisting species into horrible warped monstrosities, and in one or two occasions full-blown, not-even-bothering-with-the-technobabble necromancy. Sith Alchemy is pretty much Magic, and most writers make absolutely no attempt to justify it as some sort of biological side-result to do with midichlorians.
Subverted in the Labyrinths of Echo by Max Frei. Magic is indeed divided into White and Black, but only in terms of subject: Black magic deals with tangible materials while White one - with images, thoughts, souls and other ethereal matters.
Moreover, this means Black magic is used mostly in the kitchen or to make amulets, while strong White is what's used to make things... less corporeal. The highest-level White magic spell humans can cast is the highly destructive Green Fire: it touches anything (save strongest barriers), this something vanishes — no remains.
There are some things considered dark or forbidden, mostly those including some degrees of human sacrifice or world-ending effects.
Somewhat subverted in Michael Moorcock's Stormbringer universe - all magic is inherently chaotic, even when used by the powers of Law, but chaotic isn't inherently evil.
Avada Kedavra, or the Killing Curse, is forbidden in the same way gun control is practiced in Great Britain. High-ranking Law Enforcement "good" mages cast it as well in the Harry Potter-verse. This could be merely a sign of the overall "governmental corruption" motif, however.
Crucio, the Cruciatus Curse, not only causes pain as torture, but also will only work if the caster really enjoys inflicting pain. Righteous fury only stings a bit.
Imperio, the Imperius Curse, is a forbidden mind control spell.
There's also the Sectumsempra spell, which causes severe physical damage and cannot be healed by non-magical means.
Necromancy also exists in the Potterverse as extremely dark magic. In an interesting subversion, it's pretty much useless because the Inferi (zombies) created by it have no souls or wills of their own.
There's also the Horcrux. It requires you to do commit murder, whereby one takes a piece of their now fractured soul and places it into another object, so they may not die.
All of these fall under a branch of magic the series calls The Dark Arts, all of which seem to be this trope.
In The Second Chronicles of Thomas Covenant, the form of magic in the common use is powered by blood. Your own blood is fine, but if you want to do something moderately powerful, someone has to die. In addition, every spell cast in this way has the side effect of making life slightly worse for everyone by feeding power to bad stuff. The books also have other forms of magic used predominantly by Evil Minions.
In The Dresden Files, use of Black Magic is constrained by the White Council's Seven Laws of Magic. The most notable instances of this in the story so far (at least, in magic used by the protagonists) are using magic to kill, necromantic animation of human bodies, and Mind Control. "Reaching beyond the borders of life" and trying to "swim against the Currents of Time," among other things, also violate the rules, but may not technically be Black Magic. The difference is that Black Magic has been shown to be powerfully addictive, to the point that it's implied the mandatory death penalty for violating the Laws (except in certain, rare circumstances, namely a council member is willing to put their own necks on the line on he violator's behalf) is probably a good thing. One member of the Senior Council, the Blackstaff, is given leeway to use Black Magic when the Council really needs it. The current holder of this office is later revealed to be Harry's mentor, officially assigned to him by the Council because he's the only one who would be allowed to "put him down" if he ever tries using Black Magicagain - Harry's previous use of magic to kill was ruled to be self-defense, which means they'd at least let someone stick their necks out for him, rather than go straight to the killing.
the Blackstaff is in fact a black wizard's staff that lets the user violate the laws of magic without going all evil and crazy. Instead, Ebenezar just gets a lot of nightmares and other guilt issues, but no evil laughter.
How powerful the result of Necromancy is depends on the strength (life force) and age of the corpse. Most corpses intact enough haven't been dead all that long, so for the most part it's useless unless used on a human. Harry himself stays within the rules by using it on the complete skeleton of a sixty million year old dinosaur found in a museum.
A huge part of the reason why Black Magic in The Dresden Files is so bad is that magic in the setting is based on belief. You can't work magic if you don't honestly and truly believe in employing it both in the way you're using it and for the reasons you're using it. So, when someone uses a magical ritual designed to rip your heart out of your chest, or to invade your mind to make you a meat puppet, or to steal your body or turn you into a zombie, they can only do that because they believe that it is right for them to use that power on you in that way. There's a reason why those who use Black Magic are generally twisted and vicious and outright evil and insane.
It doesn't help either that this Black Magic is like a super-steroid for mages, 6 renegades from a neighbouring empire, where this magic is legal, curb stomp a whole nation. While the majority of mages are practically powered by AA batteries, the renegades and anyone else who practices black magic are effectively walking nuclear reactors of magic. By the end of it the guild pass a decree that effectively leaves the protagonist in gilded cage scenario, or so they wish to show to the king, every member of the guild is fully aware they stand no chance if they try to force her do something she doesn't wish to.
In Garth Nix's Old Kingdom trilogy, there is Charter Magic and Free Magic. Free Magic is used by necromancers and various non-demonic creatures. It's frequently described as having an acrid, metallic smell and being physically corrosive. Humans who dabble in it for too long usually develop some kind of horrible appearance which they can only do so much to mask. Charter Magic is generally benevolent, but a number of instances in the books point out that that it's not a toy, either (one character loses her voice for a few weeks after speaking a particularly strong spell, and is told that she's extremely lucky that she wasn't completely destroyed by it). Not so much Good vs Evil as Order vs Chaos.
The Abhorsens, whose job it is to reverse any raising of dead done by necromancers, use both without bad effects.
At least we never see it happen, although the upper example was the current Abhorsen-in-waiting. So they're probably not immune, just more careful.
Abhorsens are not immune to the corrupting influence of free magic and necromancy, just resilient and religiously committed to using it carefully and correctly. At least one of the Greater Dead is described as being a former Abhorsen, so even they can screw up and suffer the Fate Way Worse Than Death
Death magic in Lois McMaster Bujold's Chalion books hits two out of three - it summons a demon from the deity that at least some of the world's residents consider evil and has the sole purpose of (surprise!) killing the target. However, it also requires the sacrifice of the caster.
The British author Dennis Wheatley might be best remembered today for his novels dealing with Satanic black-magic cults. Christopher Lee got a rare chance to play the hero in the Hammer Films adaptation of Wheatley's The Devil Rides Out.
Robert Jordan's The Wheel of Time has the True Power, a form of magic that can only be used if a direct link to the Dark One has been forged, and then only if he decides to allow it. And the eventual fate of those who use it regularly is so terrible that only one of the baddies dares to use it at all. And that's because he's already batshit insane.
As well as the main character, due to him becoming more and more like Ishamael in goals and motivations.
Averting Moral #2, above, is basically what the whole series is working towards.
Tamora Pierce's books include, among other things, a mage who forces parents in the local village to give him their children, whom he kills so he can transfer their souls to giant, sentient, insectlike "killing devices" which he sells to a king as war weapons. Sleep tight!
In C. S. Lewis's Prince Caspian, when it looks to the members of La Résistance as if no help from Aslan is coming after all, Nikabrik the dwarf (along with a hag and a werewolf) wants to call the White Witch back to Narnia to help them instead. There's some vague talk about drawing circles and "preparing the blue fire."
In The Silver Chair, when Eustace suggests to Jill that they try to call to Aslan and see if he'll take them into Narnia, she asks, "You mean we might draw a circle on the ground ? and write in queer letters in it ? and stand inside it ? and recite charms and spells?" He admits that he had something like this in mind, but upon further consideration he decides that that's probably "all rot" and that they should just face eastwards and hold out their arms "like they did on Ramandu's island" while they appeal to Aslan.
Used by Valentin Ivashchenko: the protagonist of the Warrior and Mage series, "Black Earl" Valle, is the strongest necromancer to live for several centuries. Valle makes a major point of neither choosing a divine patron (his choices would be obviously limited) nor borrowing power from anything that will require a greater payment than he can accept, and researching any possibility to discredit this trope. Other spellcasters capable of necromancy are less ethical.
Used by Iar Elterrus:
When dealing with the new incarnation of the "Bearer of the Gray Sword", the Empire's mages unseal forbidden archives. The spell they find has to be fuelled by sacrificing 10000 humans.
In the same setting, the Empire's main magic university not only has a faculty of "pain magic", but produces devices to measure and store the pain of torture victims, just to make sure the tortures don't cut slack to anyone.
In Alexander Pehov's Sparks and Wind series, the main magic school of the Sdis empire is referred to as the "black school". Their spells revolve around necromancy, pain and torture.
Vadim Zykov's Return series:
Necromancy is the official magic of a country - the strongest necromancer is the king, and gaining ranks means gaining social standing. Spells powered by blood, sacrifice and desecration are par for the course. Most necromancers will cast a spell to return as liches after meeting an untimely end, and the liches are still partly controlled by said country.
Shamans of some human tribes possess the knowledge of the Collar and the Black Collar spells. Said spells are woven into slave collars, allowing the owner to inflict any degree of pain upon the slaves, coining the in-universe idiom "Loyalty of the Collared". Black collars are for enslaved mages - they add total blockage of magic abilities to the regular functions.
Neither the most hardened criminals nor the most ruthless warlords will harm elves. Those who do will be hunted down relentlessly and subjected to the "Forest's Breath" spell - torture and slow execution.
Worlds-travelling elder dragons don't only snack on occasional humans, they fuel said worlds-travelling by Human Sacrifice.
Regular dragons have called an undeadelder dragon to prevent the fulfillment of an obscure prophecy.
Modern Russian fantasy often takes up motifs from Fairy Tales, among them the character of Baba Yaga and Koshchey the Deathless. Baba Yaga's role varies among authors, as it does in fairy tales, from benevolent or neutral to monstrous and cannibalistic. Koshchey is usually depicted as universally evil with various powers and abilities. Either Koshchey or his followers usually fall into this trope.
In Terry Goodkind's Sword of Truth series, Magic is defined as Additive and Subtractive, with the "magic sand" for Additive magic being pure white and for Subtractive magic being as black as space.
There are three branches of magic which are classed as "black" in The Riftwar Cycle. The first, and worst, is necromancy, the ultimate violation of nature. The second is arcane life, which involves warping living things to the magician's will, and the third is demon summoning, though in that case it's not the magic itself that's bad so much as the fact that most of the things you can use a demon for once you've got it aren't very nice.
Sourcery in The Witch Watch mainly seems to be comprised as this and all magic is condemned as unholy in the eyes of the Church.
In Devon Monk's Dead Iron, Mae's magic twists to this and causes pain. She uses great care to use it only beneficially — keeping out vermin — and laborously learned to undo curses and other dark bindings.
Leo Colston in The Go Between is obsessed with astrology and the occult. At school he devises a curse on his chief bully; the boy subsequently has a serious accident and Leo gains some respect for his perceived success. He attempts another curse later; it doesn't end happily for him.
In Shadow Ops, "Negramancy" is the designation for magical ability to cause decay, rot, and entropy. By its basic nature (and the nature of Shadow Ops' magic system) magic is very powerful and requires relatively little effort to use beyond willpower and mental discipline. A powerful negamancer is a Person of Mass Destruction who kills and destroys in one of the most horrible ways imaginable, and can do this to ''anything. Tanks rust and fall apart, flesh rots off the bones, plastic breaks down, and electronics corrode. Nothing is safe, and the only shown negramancer in the series, Scylla, has an ugly steak of brutish insanity and a superiority complex that rolls together to make her one of the most terrifying things in the setting.
In Living Alone by Stella Benson, Sarah suggests World War II was caused by this. Richard rejects the notion at once.
Live Action TV
In Buffy the Vampire Slayer all magic is Black Magic, and is referred to as the 'dark arts', though some spells are more corrupting than others. In season six Willow becomes addicting to the stuff like a drug, and people freak out whenever she uses magic that does nothing more than decorate the house or levitate a book. In season seven, Willow struggles with overcoming her old habits, and briefly snaps after using a simple barrier spell.
Before Season Six, and even sometimes during, magic was often used as a metaphor for Lesbian Sex. Take that as you will.
Kyoryu Sentai Zyuranger: Bandora the Witch dabbles in it, and invokes the Darkest of Black Magic to summon her master, Dai Satan, to Earth to bolster her power and attempt to kill off the Zyurangers and Daizyujin and lay waste to the Earth.
In The Secret Circle, John Blackwell and his two daughters, Cassie and Diana all possess dark magic due to their ancestry. Dark magic is the most deadly and dangerous form of magic.
Dark Magic possess the same capabilities as regular magic, though it appears to be slightly more potent. Unlike regular magic, dark magic is not limited by coven laws, as witches bound within circles are capable of using their dark magic without collective aid. Cassie Blake has successfully performed dark magic on several occasions while bound to her circle and was also capable of using regular magic as well, revealing witches that perform both dark magic and "white magic" appear to be able to distinguish the two apart and use them separately.
Dark magic has been shown to penetrate an iron sulphate circle which is supposed to block a witch's magic while inside the circle. Cassie Blake was capable of setting a witch hunter on fire using her dark magic, despite the fact that she was inside the iron sulphate circle as well.
Dark Magic also appears to grant it's users a unique connection to other's minds, allowing them to view another's memories. Cassie Blake was able to see an apparition of Faye's memory while others could not with the exception of Faye. This connection was seen again when Cassie performed a spell to recall the "lost" memories of Jake Armstrong.
Dark magic also appears to have a unique connection with other forms of magic (though the exact nature is unknown), as Cassie and Diana were noted to be the only witches that could form the crystal skull. Dark magic mostly appears to be an innate quality, however Royce Armstrong mentioned that John Blackwell wanted to teach the circle dark magic. Because dark magic is rooted and accessed by negative emotions (anger/hate), it's possible to some degree it can be achieved by those that do not come from dark lineage like the Blackwells.
Dungeons & Dragons has some spells designated as "Evil", pure and simple. Typically, they're the spells that are designed to subvert or counter "Good" spells, torment or exploit others, or that require truly nasty things to operate — primary Evil spell components include mortal souls and the body parts of angels (except for feathers, which when given willingly are powerfully Good items).
3E sourcebook dedicated to Evil character options, The Book of Vile Darkness, includes a whole chapter of these. The page picture comes from it - it's the Prestige Class dubbed "Demonologist".
The above no longer applies to the 4th-edition — any mechanical effect of alignment (such as good or evil) has been removed. However, the Dungeon Master's Guide does advise that Evil aligned divine-magic spellcasters should have their powers reflavoured to be more dark and sinister.
In the Ravenloft setting, Black Magic generally involved a Powers check, and may be stronger than in other D&D game-settings. Hags and shadow fey are notorious practitioners of such magic.
According to TSR's Marvel Super Heroes RPG, Mind Control was considered a villain's power, and if a hero ever controlled another character's mind, he would lose Karma (the game's equivalent of hero points and/or Experience Points), not only for the act itself, but for any negative actions committed by the controlled character. Sadly, most player characters had randomly generated stats and powers.
Amusingly, the Marvel Super Hero named "Karma" has the power of Mind Control (called Possession — but it works like mind control, really).
In Shadowrun, the government of Aztlan (formerly Mexico) is involved in the use of a nasty version of blood-powered magic which is a deliberate corruption of old Aztec rituals. The game has also featured toxic shamans, who seek patronage from toxic spirits and are considered walking fallout.
Actually in Warhammer all magic comes from the domain of Chaos. Whether it's Black or White Magic depends on how you use it.
The Dark Elves in Warhammer Fantasy get the Lore of Dark Magic, which contains powers of the body-freezing and soul-stealing sort. The Vampire Counts' and Tomb Kings' Lore of Necromancy (or whatever it is called) also qualifies.
Strictly speaking, the term Black Magic in Warhammer only applies to acts of illegal magic performed in the Empire, by people without Diplomatic Immunity. It covers magic powered directly by one or more gods whose worship is forbidden in the Empire (usually Chaos, but Khaine and others pop up occasionally); Necromancy (not to be confused with DeathMagic); witchcraft; spells powered by more than one Wind of magic (which can include both Dark and High Magic); daemonology; virtually everything to do with warpstone and any arcane magic performed by someone who doesn't hold at least an apprenticeship in one of the 8 Colleges of Magic. Outside the Empire, it's more of a colloquialism.
Magic: The Gathering's black cards dip into this, although considering that the game is all about wizardly duelling and we consequently see mainly the martial aspects of any of its colors this is mostly a matter of flavor. (Black does, however, have something of a monopoly on discard effects — implied to be actually harmful to the target's sanity — as well as ones that reduce the opponent's life total directly without technically inflicting 'damage', sometimes allowing the caster to gain those life points for him- or herself vampire-style.) However, any colour has the potential to be good or evil—black can be classically "evil", white can be fascist, red can be chaotically destructive, blue can be immorally detached from reality (think Josef Mengele), and green can be cancerously uncontrolled.
On the subject of sanity-damaging magics: Memory Erosion, Sanity Grinding and Traumatize are all blue, while spells that directly hurt both you and your opponent, possibly along with any creatures in play, are red.
To expand a bit: Black magic is considered to be "destructive and costly" instead of outright evil. The difficulty is that many evil beings go straight for it. It has a variety of effects (dipping into turf owned by most colors) and often requires sacrificing your life (or somebody else's...). Black cards tend to be greedy or selfish, but no more so than, say, Capitalism. It embraces both the best and worst aspects of self-interest. However, this trope is partly averted in that many Black creatures and spells are not evil, just aggressive or unhelpful, and there are many unpleasant beings associated with other colors.
Toshira Umezawa was created specifically to be a black-aligned main character. While he wasn't the most good protagonist, he tended more towards selfishness than evil. Wizards explains that black's "good" aspects (in terms of Western values) tend towards capitalism and other forms of competition.
Mage The Awakening has a morality system that heavily penalizes certain acts, such as using mind control and ripping away a person's soul. Then there's using the Abyss to fuel your magic, which basically means paying favor to something that is to reality what anti-matter is to matter. Finally, there are the Left-Handed Paths, Legacies that involve incorporating magic that is both destructive to others and, ultimately, yourself into the very pattern of your soul. Such Left-Handed Paths include people who worship the Abyss, necromancers who maintain immortality by feeding on people's souls, Knight Templar psychics who project themselves into the minds of Abyssal beings in order to find out what they fear, and devout individuals who see nothing wrong with subjecting mortals to Mind Rape in order to get a glimpse of the "angels" who predated existence.
Dark Thaumaturgy from Vampire The Masquerade is a demonic offshoot of the regular Tremere Discipline of Thaumaturgy (vampiric blood sorcery) that used to be practiced by the Tremere Antitribu of the Sabbat before they were all destroyed. Quite simply, it is Thaumaturgy learned from the demons of Hell. Vampires who mess around with the stuff are called Infernalists, and they range from fools who think they can outsmart the devil, fools who want a quick path to power, and those too weak to resist infernal temptation. Infernalist unlife expectancies are rather low, both due to the inherent dangers of dealing with the infernal and because the Sabbat Inquisition is ruthless about dealing with those who truck with demons in general.
Black Magic — defined primarily by source — typically isn't available to Player Characters in Deadlands. After all, you're supposed to be fighting pawns of darkness, not helping them. There are PC-approved "Gray Magics" that can be used; wily Hucksters make Bets WithThe Legions of Hell, with the caveat that they never intend to lose. Syncretic religions like voodoo and the Aztec-Catholic blend Anahuac have adherents that can do unseemly things with a death motif, but the practitioners aren't necessarily bad people, just...very different. Then, there's Whateley clanblood magic. (That last one can still cost you your soul if you're not careful.)
The anthropomorphic RPG Ironclaw has the Necromancer class, specializing in bringing about a Zombie Apocalypse, energy draining, Mind Rape, and other nasty things. However, this class is hidden in the back of the book with a warning to Dungeon Masters not to let players pick it arbitrarily. Why? Because if a Necromancer rolls three sixes in any of their tests, the DM is encouraged to think of random disasters to befall them.
Sorcery in Blue Rose is roughly defined as "any magic that alters the will or form of another being without their consent." Using too much of it deteriorates your physical and mental health until you go insane or waste away from sickness... unless you give in to the corruption, in which case you become more fit and powerful than ever but also become evil.
In the Star Wars d20 RPG, characters with at least one level in a Force-using class can choose to call on the Dark Side to augment their abilities, and some Force powers are inherently "dark," such as Force Lightning. Characters who have "fallen to the Dark Side" automatically use Black Magicevery time they tap the Force.
In Forgotten Realms, up until 4E most spellcasters, whether good or evil, drew their spells from the Weave. Then one of Mystra's rivals, Shar, created an anti-Weave called the Shadow Weave, which is chiefly used by evil spellcasters. In 3E, the Shadow Weave existed but was under Shar's control, so very few mages were interested in using it.
At the boundary between 3.5E and 4E, Shar helped Cyric to assassinate Mystra in an attempt to wrest control of the Weave from her. The attempt backfired: killing Mystra destroyed the Weave (sparking off the Spellplague) and cost Shar control of the Shadow Weave.
The Final Fantasy series is an aversion. Black magic is just offensive magic, and users tend to be no more or less evil than any other characters. Black mages, such as Rydia, Vivi and Lulu tend to be nice people (Lulu is a little cold, but entirely wholesome).
Riku of Kingdom Hearts struggles with true Black Magic throughout the games. He argues that the ends justifies the means and using Dark magic for good reasons is okay, and this has different results in the different games.
It can be convincingly argued, however, that overall it was far more trouble than it was worth and he was much better off avoiding it, especially as he would have gotten "Light Side" powers of comparable potency for much less grief.
Eventually he decides to use both, which changes his rather evil sword into a keyblade. The keyblade has both "evil" and "good" symbols, like a devilish wing and an angelic one. The balance between light and dark is called Twilight.
It's implied that "twilight" is closer to the dark side. At the end of Chain of Memories, Di Z asks Riku if he is taking the road to twilight and downfall, after Riku refuses to take the road to light or darkness. In reply, Riku states that he is taking the "Way to Dawn" (or road to dawn in the English translation, but it was suppoed to be Way, since it worked as a double meaning with taking the actual path as well as taking the Keyblade "Way to Dawn.")
Subversion: in Fire Emblem, dark magic isn't necessarily reserved for evil characters, and you can have good-hearted Shamans, Druids and / or Summoners in your party. Their dark spells are usually more powerful than the usual, but are extremely slow as well; also one of them, the Nosferatu magic, can steal hit points from the enemy and heal the caster's previous wounds (Note about this spell, it was originally called "Resire", and was Light Magic, it returned to being Light magic in the Radiance games, albeit much weaker. However, the effects of dark spell generally differ quite a bit from the basic "deal damage" spells that the Light and Anima branches have. For example, Eclipse halves enemy hp, Luna pierces resistance... and so on. Notable dark magic users are:
Genealogy of the Holy War has Big Bad Manfroy (Dark Bishop) and most followers of the Religion of Evil, the Loputo and Dark Mages. And of course, the "Messianic" figure of said religion, the Dark Prince Yurius. (Yurius's Loputousu tome is also the nastiest Dark Tome in the series (on top of being a Tome of Eldritch Lore in its truest form) — while it appears to be the weakest of the Game Breaker Holy Weapons (It's only Stat Bonus is + 5 Res), it halves the stats of anyone who dares fight Yurius, unless he/she is wielding the stupidly broken Naga tome.)
Fel energy in Warcraft. It fuels the Burning Legion's destructive crusade, gives warlocks their power, and when mortals overuse it, they tend to mutate, becoming over-muscled and violent caricatures of their former selves who only crave more power. It also has a nasty effect on the environment, turning the landscape into a Garden of Evil or simply killing flora & fauna.
However, in World of Warcraft, the playable warlocks can be as good as they like, while every other raid boss's insanity is explained with a "he used fel magic and went insane".
Similarly, death knights spread diseases, summon undead, and similar necromancy-based techniques, but they aren't necessarily bad or evil. However, there are quite a few undead enemies, some of them even being death knights themselves. Tthe player death knights regained their own free will after being betrayed by the Lich King.
It's notable that both the above classes, lore-wise, are hated by pretty much everybody they meet. NPC's generally don't mention it because their dialogue doesn't vary that much between different players, but to give a hint, a Gnome warlock will be sent to Stormwind to train because their leader was kicked out of Ironforge, and then if you ask a Stormwind guard where the warlock trainer is he replies that nobody like that would be allowed in the city, but that there has been some demonic activity around one tavern (where the trainers are hiding in the basement).
After the Wrath Gate incident, the Undercity's abominations are replaced with Kor'kron Overseers who if you ask for the location of the warlock trainers in the Undercity they will give the response "You'll find the warlocks in the Magic Quarter's main building, but I better not hear of any trouble that comes of this." Unless you are undead then you can get a message that is even more filled with malice "You have guts asking me about warlocks. Go to the Magic Quarter's outer ring and get out of my sight." It is makes a lot of sense though considering demons were very much involved with the reason why they're there watching over the undead.
Malygos gets a free pass there as he is the Aspect of Magic and thus immune to its corrupting effects due to having complete and total control over it, killing him would be extremely bad for all Arcane magic (and its users). His decision to kill everyone who uses Magic is an overreaction to the situation, since the last time he remembered mortals running around using magic Sargeras very nearly invaded the planet. Being immune to Arcane Magic corruption and being in charge of its usage, he's allowed decide how it's used since arguably he's the only creature on Azeroth who actually knows what he's doing.
In Soul Nomad & the World Eaters spellcraft that uses Crimson Tears (basically the condensed souls of particularly strong-souled individuals, created through their deaths) is considered Black Magic. Yet, because only Crimson Tears grant the power necessary to do things like fusing humans and gods together, resurrecting the dead and creating barriers capable of imprisoning the World Eaters, they are heavily used by most powerful magicians, including some of your allies. They have no side-effect apart from the ghastly material component.
Street Fighter has the Satsui No Hadou, or "Surge of Murderous Intent", a dark power which can be used for deadly moves like the Shun Goku Satsu. Akuma and Evil Ryu represent characters who have succumbed to the power of The Dark Side.
In Florensia, the Saint class can change to a Priest who focuses on "light" magic such as healing, resurrection, and defensive spells, or a Shaman who uses "dark" magic mostly consisting of offensive and weakening spells.
In Battle for Wesnoth, black magic is pretty much synonymous with necromancy, and hence evil.
Dominions has death magic (about half of its spells fall under this) and blood magic (every single spell requires human sacrifice). One death magic global enchantment, Well of Misery, subverts the trope by concentrating a portion of the worlds negative energies into a single source. In essence, the caster gets an income of twenty death gems per turn while crop yields increase all over the world.
Necromancy in The Elder Scrolls is seen as this. Oddly, Conjuration (summoning demons/zombies/ghosts, etc) is perfectly acceptable.
In Morrowind an orcish necromancer will rant about the hypocrisy of the natives, who ban philosophical necromancy, yet summon their own ancestors' ghosts and various undead to guard tombs. The natives do judge necromancy by subject: working with your ancestors is fine, disturbing unrelated dead is a crime.
This conflict was meticulously hand waived in one of the books in Oblivion. It is a description of the lengthy debate by senior Mage's Guild members on banning Necromancy, and when one of the defenders pointed this out it was decided that while some schools technically overlap, the practicing of Necromancy itself required the user to go too far. However, it is implied that the Council of Mages was playing with loaded dice, as previously in the series history the Empire considered bodies and souls personal property to be willed away to whoever the deceased would.
In Skyrim, most Daedric rituals require human sacrifice in exchange for mightily enchanted equipment. The Greybeards also consider the Shout Dragonrend to be this.
City of Heroes has multiple "Dark" themed Powersets in Melee, Ranged, Defensive, and Support flavors. These powers typically involve sapping the lifeforce out of foes or doing other spooky things, but they're available to heroes as well as villains.
Arcanum has Black Magic as one of the available schools. That's pain and necromancy with all the prejudice from the general population, although the school doesn't own the game's strongest destructive spell.
In the original Super Mario Bros. the Koopa are (apparently) highly skilled in Black Magic. While this is dropped in later games Magikoopa and Bowser retain their ability to use magic.
Wizards and Mages in Ogre Battle: The March of the Black Queen. What they use is basic fantasy magic, involving blasting targets with elemental spells (of any element except Light, including Physical). Nonetheless, this is one case where wizards are indeed evil, or at best Noble Demons: Wizards and Mages must have a low alignment to take the class (but not too low), and can recruit demonic units to their side. Furthermore, being a Mage is a prerequisite for becoming a Sorcerer, which is the game's term for a Necromancer.
Sorcerers and Liches also use Black Magic and upgraded versions of Mage attack magic, but they lose the ability to deal with demons. Instead, they raise undead to fight for them.
Dark Magic in Might And Magic is not necessarily entirely evil (the game that introduced it pointed out that it is how you use it that is most important in deciding the morality of it), and there doesn't seem to be real difference in source between it and Light Magic, but otherwise it fits — most users are evil sorts (but there doesn't seem to be any corrupting effect involved, more a correlation between being evil and being the sort attracted to using Dark Magic), the spells do things like drain the life-force of everyone in front of you, sacrifice a hireling for health, animating the dead, throwing a cloud of death at your enemy...
In Dark Soulsnormal sorcery is this, especially the higher level spells you get from Big Hat Logan. The game doesn't state what exactly is going on here, but sorcery was invented by an insane undead dragon and is closely related with the power of souls somehow.
The Artorias of the Abyss DLC goes a step further by having there be literal black magic, which is implicitly linked the the Dark Soul and is strongly linked to humanity.
As a rule, pretty much any magic used by demon cultists and summoners in the Diablo universe will be some form of Black Magic. The Dark Coven led by Maghda from Diablo III, for example, uses human suffering through Cold-Blooded Torture and Human Sacrifice to their demon master Belial to fuel their magic, most of which involves summoning demons.
In Sluggy Freelance Gwynn has a number of magical abilities. However, since she got those abilities from "The Book of E-Ville" and a subsequent possession by a world devouring demon, she doesn't use them that often since there's a lingering fear they'll bring the demon back again.
Black Magic in TwoKinds is far more powerful, able to bring the dead back and rip souls apart, however it's very hard to control, drains the life around the user, and tends to drive said user crazy (and casting a spell can kill the user) but nothing Laser-Guided Amnesia can't fix.
It's ability to resurrect is only theoretical. In practice, it takes much more power than can be successfully channeled by even the most competent magicians.
Infernomancy: By making a contract with a demon lord, an Infernomancer gains powers that vary from demon to demon in addition to the standard Hell Fire. An otherwise unnamed Infernomancer in the early chapters, prior to breaking free of his contract, bound to the Demon of Wounds, is immune to physical damage except for the self inflicted Eye Scream. An infernomancer bound to the Demon of Greed works with ambitions and desires; an infernomancer bound to the Demon of Treason works with seduction, corruption adn betrayal. Large-scale infernomancy by those bound to the Demon of Poison creates results similar to nuclear fallout over a country, and would ultimately allow a Demon Lord to physically manifest in the world.
Black Mage in 8-Bit Theater. His Kamehame Hadouken is powered by love. Because it drains the world of love every time he uses it! This is to be taken literally, the divorce rate increases measurably every time he casts it.
Played with in Tales of MU. On the one hand, necromancy is considered a legitimate speciality for aspiring wizards as long as they follow the rules. On the other hand, the only necromancy student we ever meet is Steff, who hates most of the world and plans on going off to live with an ogre prince, where she won't have to follow any regulations and will also act as his official torturer. At one point, she mentions the possibility of having sex with Mackenzie's reanimated corpse should Mackenzie die prematurely. On the third gripping hand, in many other ways Steff is given a very sympathetic portrayal.
We see Hekate doing this in the Whateley Universe. She's got the whole thing down. She does a spell that summons a demon, requires the soul of one of the people in the circle, gains three boons from the demon, and ALSO forces the survivor in the circle to do three things Hekate will ask for in future. Whew.
What's worse? She gets it from Cthulhu and friends! If there's ONE thing worse then 'demons from hell'...
The Whateley Universe also features the Necromancer (who's just as bad as one might expect, has his own cosmic connections, and is also Carmilla's uncle), and the Grand Hall of Sinister Wisdom, basically a modern-day guild for villainous 'black' magicians.
Katara learns to control another human being through "blood bending". The witch that taught her this used it almost exclusively for evil, but Katara was forced to use it for good (or neutral) in order to save Aang and Sokka. However, it could easily be argued that it did corrupt her, as later in the same season, she used blood bending to extort information out of a Fire Nation officer in a quest for revenge.
By The Legend of Korra, bloodbending has been completely outlawed through the efforts of Katara. A crime boss named Yakone used it to terrorize Republic City, but soon has his bending removed by Aang. Yakone escapes to the Northern Water Tribe where he starts a family and teaches his sons, Amon (born Noatak) and Tarrlok, how to bloodbend. Amon eventually leaves his father while Tarrlok stays behind. Years later Amon figures out how to use his bloodbending to take away bending, while Tarrlok becomes the Northern Water Tribe representative in Republic City. Both use their bloodbending to subdue their opponents. Amon eventually develops the craft to remove bending from an individual.
In the third season premiere of My Little Pony: Friendship Is Magic, Twilight Sparkle has to duplicate the spells used by King Sombra, the cruel and heartless once-ruler of the Crystal Empire, to find where he hid the Crystal Heart. Every time she does, her magical aura turns pitch-black and roiling instead of its regular color, and it seems to cause her a great deal of pain.