Lady of Black Magic

She's elegant, she's composed, and she's graceful. She's also packing enough magic to level half a city. The Lady of Black Magic is a character type found in fantasy who is primarily an offensive magic user.

Personality-wise, a Lady of Black Magic is stately and more mature than The Hero. She may be an Ice Queen.

In design, this character will almost always be wearing something feminine, usually a dress of some sort. Unlike the Lady of War, the Lady of Black Magic can be Ms. Fanservice.

Physically, she'll be weaker than the melee type fighters, and will usually be equipped with a rod or ranged weapon. Very rarely she will have a melee weapon, but it will be weaker or less impressive than the hero's. Her primary combat role is to unleash destructive Black Magic, although she will occasionally have secondary healing, buffing, or debuffing abilities, as well.

Ladies of Black Magic are Always Female, unlike their counterparts Black Magician Girl and White Magician Girl. She is rarely a Love Interest for The Hero, although if she is it will often be part of a Defrosting Ice Queen plot. Instead, she's usually older than The Hero and fills the role of a bigger sister, often a Cool Big Sis, or maternal figure.

Subtrope of Black Mage. Compare to Black Magician Girl, the other stock character type for offensive mages in fantasy. Contrast White Mage and White Magician Girl, to whom this character type is often a Foil, and Black Magic.

Examples of Lady of Black Magic include:

Anime and Manga

Urd from Ah! My Goddess.
Words Worth: Maria is a stately example, garbed in an elegant white robe (though it has split seams, showing plenty of leg), a sea green cloak, and sandals.
Both Miyu and Reiha from Vampire Princess Miyu, as they both are very elegant and reserved as they attack their enemies with fire (Miyu) or ice (Reiha)
As shown in the page image, Adilicia Lenn Mathers from Rental Magica combines power and elegance as the heir to the demon-summoning magic of Solomon.

Comic Books

Sistah Spooky from Empowered.

Film

Luster in The Gamers: Dorkness Rising seems to be an attempt at this archetype, but her player isn't very good at the whole "dignity" aspect.
Claudia's mother in Snow White a Tale of Terror is implied to have been one.

Live-Action TV

In the 1998 Merlin series, Mab fills this role, as well as being the series' Big Bad.
In the BBC Merlin, it was Morgause, until she died and Morgana stepped up to the plate. Word of God says she's at least as powerful as Merlin now.

Literature

Nicci of the Sword of Truth, a former Sister of the Dark who functions as one of Richard's primary magic experts, and is also the team expert on Subtractive Magic.
Dragaera's Sethra Lavode is a 250,000+ year-old undead sorceress, and contrary to the trope description she couldn't just level half a city—she could probably cause The End of the World as We Know It.
Melissandre the Red from A Song of Ice and Fire fits the personality aspect (and becomes something of a mentor to Jon Snow during A Dance With Dragons), but as part of a low-magic setting she's limited to soothsaying and summoning creepy shadows. Given that she's one of a handful of people to show outright supernatural abilities at all, however, that says something.
The White Witch in The Chronicles of Narnia: The Lion, The Witch and the Wardrobe qualifies as well. She goes into battle wearing Aslan's mane as a pelt and fighting Florentine style with two swords and turning anyone who crosses her path into stone.
Matilda in The Monk. She's a woman of many talents.
Medea from The Icemark Chronicles.
Skuld, a half-elven sorceress from the 13th century Saga of Hrolf Kraki.

Music

The eponymous "Devil Woman" from the song by Cliff Richard.
The Eagles, "Witchy Woman".

Video Games

The Final Fantasy series has liked this trope in recent games.
- Lulu from Final Fantasy X, of the Ice Queen variety. Also somewhat gothy.
- While she may not match most examples in height, she more then substitutes pure might. With ladylike grace and magical fire, Shantotto is to what this trope aspires! Oh Hohohoho!
- Edea, Ultimecia, Adel, and some other unnamed Sorceresses from Final Fantasy VIII.
Fatima, the antagonist Witch of Luminous Arc 2, adequately mirrors the cheerful Althea. Arguably the most powerful Witch, her ability to mercilessly wreak havoc with Shadow Frost magic is only equalled by another spectacular demonstration of her "power".
Celine from Star Ocean the Second Story.
Mitsuru Kirijou in Persona 3, who is one of the best magical attackers in the game. Likewise, Persona 4's Yukiko Amagi, but she also crosses this with White Magician Girl.
Dragon Age has Morrigan, a shapeshifter who is well-spoken and cutting—and evil. In the Dragon Age toolset, she's also listed as one of the few characters with "High" intelligence, and her biography notes that she favors a look of wild elegance. She's the most evil member of the party, and NPCs often comment she's very beautiful.
Jessica from Dragon Quest VIII. Although she's a little more fiery than this trope typically is, she has a rich upbringing, possesses a sharp tongue backed by a British accent, and generally has an overall bearing that's more lady than genki. Also her penchant for fanservice is an actual game mechanic.
Millenia from Grandia II. The twist being, she's the Super-Powered Evil Side of the White Magician Girl, Elena.
Femme Fatale Evil Cleric Defector From Decadence Viconia from Baldurs Gate II.
Radiant Historia has Eruca, a reserved literal Rebellious Princess who packs some of the most powerful offensive magic in the game. Raynie is a partial example, having the grace in battle and offensive power of a Lady, but being slightly more rough around the edges than is typical for this trope.
Jaina Proudmoore from the Warcraft franchise.
Not yet playable, but Nine/Konoe A. Mercury from BlazBlue is a very much one. Although she subverts it by having quite the fiery temper for personality.
From City of Heroes the Lady Grey, supreme commander of Vanguard. Easily the most powerful wizard in the whole game, ever composed, ever graceful and one wicked Dark Defender
Many female anima magic users from the Fire Emblem sagas:
- Seisen no Keifu: Hilda (villainous example), Ishtar. Possibly Aida, too.
- Thracia 776: Miranda, Olwen, possibly Sara and Linoan.
- Fuuin no Tsurugi: Niime, Druid!Sophia, Princess Guinevere when you unlock her. Maybe Cecilia and Valkyrie!Clarine. Sage!Lilina has the skills, but attitude-wise she's more of The Messiah. Bruhnya is an Anti Villainous version.
- Rekka no Ken: Sonia and Ursula, both villainous examples. Arguably, Valkyrie!Priscilla is one on your side.
- Sacred Stones: Lute, specially if a Sage. Also the promoted L'Arachel, though she's more... expressive than others. Selena follows it wholeheartedly.
- Path of Radiance - Radiant Dawn: Sanaki, for some. Also a well-trained Ilyana.
Rift has Asha Catari.
Servant Caster from Fate/stay night to a T.
Aqua, from Kingdom Hearts is a hybrid between this and Lady of War.
Touhou has Mima and Byakuren. Byakuren is a major subversion, though.
Miranda from Mass Effect 2 is the sci-fi equivalent, a powerful biotic, a Lady of War and the Illusive Man's top Operative.
Rose from Street Fighter is among the closest to this trope that you'll find in fighting games.

Web Comics

Rose Lalonde, from Homestuck becomes this after upgrading her weapons with Eldritch Powers.
Miranda Io from No Songs for The Dead has great potential in Black Magic, which she genetically inherited from her mother Lilith.
Magick Chicks has Anastasia - mom of Melissa, who apparently taught her both fashion style and witchcraft.

Western Animation

Raven from Teen Titans, despite being younger than average for this trope, is Wise Beyond Her Years, and her aloof personality is more in line with this trope than Black Magician Girl.