In the world of anime, shadows are sometimes treated as one of the main elements and a power that characters can control. Shadow magic is often associated with villains, but it's not unheard of for good characters to use it as a power, especially in stories that emphasize how it's wrong to judge by appearances.
Because shadows are produced by light, it's also not unheard of for characters to combine the two seemingly opposing forces into one or for characters who control such opposing forces to work together. It's also not unheard of for a series to treat power over shadows and power over darkness as separate concepts.
10 Yu-Gi-Oh!: Yugi Masters Darkness With Dark Magician
The Dark Magician card, a Spellcaster type of the Dark attribute, is a prominent Ace Card, or signature card, for both Yugi Muto and Yami Yugi. He is also associated with his protegee of sorts: Dark Magician Girl.
In the anime, his most famous attack is arguably his "Dark Magic Attack," which the anime visualizes by having him invert colors around him as hits his target. Possibly hinting at the duality of darkness and light, he once attacks with beams of light that turn black during said inversion.
9 Pretty Cure: Cure Black Controls Black Thunder & Black Pulsar
Cure Black is one-half of the original magical girls that started the Precure franchise. She and Cure White combine their powers in their "Marble Screw" attack. Both girls call upon the powers of "Black Thunder" and "White Thunder," which retract into their hands, which they can then shoot at their opponent.
They also have the "Rainbow Therapy" attack, which calls upon the powers of "Black Pulsar" and "White Pulsar," which is used when they need to purify their opponent. It's also notable that the girls don't actually kill their targets, instead sending them into a void of darkness. And this isn't a euphemism: the girls are even able to talk to characters sent there.
8 Cardcaptor Sakura: The Shadow Card Is Separate From The Dark Card
Many elements and powers are reflected in the Clow Cards, and shadows are no exception. The Shadow Card is capable of controlling the shadows of both people and objects. It can also be used to hunt down people through their shadows. It can touch others but only be touched through powerful magic.
Notably, the Shadow Card and the Dark Card are separate entities. The latter and The Light card are treated as sisters and the two appear to have a close bond, to the point they cannot use their powers without the other's help.
7 Hell Girl: Ai Enma Has Dark Powers As Part Of Her Job
Part of being the titular Hell Girl gives Ai Enma a variety of supernatural powers, most notably being able to drag people to Hell. She has also been shown to attack with lethal blasts of black energy, which are implied to be powered by pain and hatred.
When particularly enraged, she even surrounds herself with purple energy. She notably uses this power to attack the Shibatas, where the energy seems to take a physical form, pushing her targets into nearby water. Other powers she has been shown to have included creating illusions and conjuring fire.
6 My Hero Academia: Fumikage Tokoyami Can Animate Shadow Monsters
Fumikage Tokoyami has the Quirk of Dark Shadow, which allows him to create an animated shadow monster that he can summon and contract at will.
This shadow does have its weaknesses. Naturally, it cannot survive in bright light and it also retracts into his host's body if it runs out of energy. That said, being in complete darkness isn't necessarily an advantage, as it gives the shadow more freedom to act on its own, making it harder to control.
5 Naruto: Shikamaru Has A Few Shadow-Based Techniques
In the Naruto universe, the manipulation of shadows seems to be a common component of the Nara clan, with Shikamaru Nara being shown as a frequent user of such abilities, their signature technique being the Shadow Imitation Technique, in which a target is restrained by the merging of shadows.
It also has the offensive variation: Shadow–Neck Binding Technique. Another similar jutsu is the "Shadow Stitching Technique," which impales a target with tendrils produced from the user's shadow.
4 Yu Yu Hakusho: Hiei Combines Fire & Darkness In His Dragon Of Darkness Attack
Fire is often treated as the opposite of darkness, but this isn't always the case, After all, smoke rises from a flame, it casts a shadow, and it's blinding to the eye, so it's not unheard of to conflate the two together.
Hiei from Yu Yu Hakusho might be such an example with his Dragon of the Darkness Flame. For this attack, he conjures black flames from the Spirit World itself, which then takes the form of a dragon and burns up anything in its way. It's also considered one of the most powerful attacks in the series.
3 Black Clover: Nacht Faust Uses Shadow Magic & His Twin Uses Light Magic
Nacht Faust is able to use Shadow Magic, which grants him the ability to control shadows, which extends so far as to let him use them for transportation, immobilize people through their shadows, and even bind targets with shadows.
His magic is used to contrast his brother Morgen, who uses Light Magic. Interestingly, Dark Magic is treated as a different power, belonging to Yami Sukehiro, which is also shown to have something of a contrast with Light Magic.
2 One Piece: Blackbeard Can Practically Become A Black Hole
Marshall D. Teach, also known as Blackbeard is one of the only characters known for wielding the power of two Devil Fruits. The Yami Yami no Mi fruit gave him the power to create and manipulate darkness, resembling black smoke. He can transform his body into darkness, but his is not intangible. Similar to a black hole, however, this ability does grant him an infinite amount of space within his body. This power also gives him some control over gravity.
Thanks to the Gura Gura no Mi Devil Fruit, he also has power over earthquakes and shockwaves.
1 Durarara!!: Celty's Shadow Power Is Very Versatile
Celty, the headless heroine of the series, is capable of strong shadow manipulation. She can use this to create weapons, notably her scythe, and bind her enemies. The series treats this as very useful magic, as she can use this for practical things like changing her clothes or even improve her typing.
Interestingly, Celty's magic doesn't seem limited to the amount of light and darkness in a given space, meaning it's just as powerful any time of the day.