The Magic Comes Back

One day the magic will come back, all of it. Everyone will be just like they were. The shadows will part and the skies will open wide. When he rises, everyone will see.

—Sandal Feddic, Dragon Age II

The past was an exciting time to live in: Magic was real, mythological creatures roamed the Earth, and humans lived side by side with elves, dwarves, hobbits and the rest. Such a shame that it didn't last and we're stuck with plain, old boring mundane life.

But wait, reports are coming in that something strange is happening all over the planet: Mysterious creatures thought only to exist in storybooks have been sighted in isolated areas and their numbers are increasing with each passing day. Some humans are starting to exhibit fantastical powers that science can't explain. Strange, yet familiar humanoid beings have been seen going about their daily lives in the middle of human cities.

What's going on? Why, the exact opposite of The Magic Goes Away. Maybe it completely disappeared at one point or maybe it didn't exist at all. Regardless of the past situation, however, magic is back and, as a result, can often pave the way for an Urban Fantasy setting.

Sometimes technological prowess will directly lead to Magic From Technology.

This trope seems to be about evenly split between ending and beginnings. As such there may be unmarked spoilers. The presence of names on this list may in and of themselves constitute spoilers.

Anime and Manga

In Berserk, the appearance of the fifth God Hand, Femto, and his rebirth as Griffith caused a chain reaction that slowly drew the supernatural world into the human world. The final and permanent change occurs during the climax of the battle with Emperor Ganishka when the two worlds suddenly become one. Cue astonished reactions from two lumberjacks as they then witness a herd of unicorns stampeding away from a hydra.
Yokohama Kaidashi Kikou combines this with a Just Before The Cozy Catastrophe setting. It's the twilight of humanity, and as cities slowly shrink, roads gradually fall into disrepair, and the human population dwindles, magical creatures and mystical phenomena are quietly coming back to the world—in a gradual and completely non-threatening way, of course, as befits the atmosphere of this work.

Comic Books

The upside of The Rapture in Therefore Repent!
A Return of Magic was foretold by Ancient Gina in Gold Digger.

Film

The 1977 animated film Wizards has humanity being wiped out in a nuclear war. Over time, mystical races such as faeries and gnomes awaken from their long slumber and return to the world bringing magic along with them.

Literature

The main plot of Jonathan Strange & Mr Norrell.
In Simon Hawke's The Wizard of 4th Street novels, magic was once a driving force in the world, based around those descended from a long-lived magical race. But some went mad with power and had to be locked away. Cut to Twenty Minutes Into the Future: after Merlin comes Back from the Dead and those of magical bloodlines are found and trained as new wizards, the world becomes a better place, and magic-powered technology replaces the old polluting resource-hogs of today. But it still has its problems, especially when some of the more troublesome immortals are revived by the sudden increase in magic.
Winter of Magic's Return and its sequel by Pamela Service are YA novels about a reawakened Merlin in an After the End setting where magic is starting to replace technology again.
Something rather like this is the undercurrent of the third book in C. S. Lewis' so-called [[Space Trilogy]], That Hideous Strength. By the end of the story, major elements from Celtic -- and to a lesser extent, Greek -- mythology are running around parts of 20th-Century England; per Lewisian reckoning, these are benevolent, quasi-divine entities aligned with Heaven and mistaken for deities by pagans in times past. The overall effect is similar to what one would expect of the reincarnation of King Arthur, which it sorta is.
At the beginning of Monster by A. Lee Martinez, magic is slowly declining as humans lose their ability to comprehend it. However, when Lotus is killed, the Cosmic Keystone she was feeding off is free to balance the universe again, allowing magic to return: not only do magicians become more powerful than ever before, but Muggles become capable of witnessing magic without any form of Weirdness Censor.
In A Song of Ice and Fire, magic is considered a folk tale by most of the people of Westeros, and no provable sorcery has been practiced in years. Then, at the end of the first book, Daenerys uses the principles of blood magic to hatch fossilized dragon eggs, and with the return of the dragons comes a boost in the general level of magic, which is especially noticeable for pyromancers and red priests.
According to author Brandon Sanderson, this will be one of the things explored in his ten-book epic fantasy series The Stormlight Archive (of which only the first has been published so far) in part as a reaction to so many epic fantasies he read in his youth being about the inevitable loss of magic and wonder. In his new series, the world will rapidly become a lot more fantastical, new races will be discovered, and wonderment will increase.
- This is pretty much what happens at the climax of Elantris, though it was only AonDor that had gone away in the first place; the other two magic systems were working just fine.
The knowledge of magic is slowly coming back in the Shannara series. It only took several false starts, almost apocalypses, and one actual apocalypse.
Pretty much the point of The Age of Misrule.
The conclusion of Legacy Of The Darksword.
The Fall of the Kings: The previous two books in the series had no magic, though some of the related short stories had minor fantasy elements (like the appearance of St. Vier's ghost in "The Death of the Duke"). Then in The Fall of the Kings, it's revealed that in the setting's distant past, before the monarchy was overthrown, the country was ruled by a series of kings and their wizard lovers, though the existence of real magic has been covered up by Internal Retcon. One of the main characters is a descendant of the ancient kings (and heavily implied to be the Rightful Heir), and the other is a scholar obsessed with the wizards (who successfully performs magic before the end of the book). Different from most examples in that this does not lead to a worldwide renaissance of magic; it might have, except the scholar gets murdered the first time he does magic in public.
Common in the Dungeon Punk genre. A good example is the Lord Darcy stories, which take place in an Alternate History where a chance scientific breakthrough lead to the codification of magic around 1300, the practice of which inevitably spread to every corner of the world.
Although magic is still around in Discworld, it is a pale shadow of what it once was, and comes with so many disadvantages that it can never be functional. The plot of Sourcery is about the old Wild Magic of the Sourcerers coming back, and why wizards gave it up in the first place.
The Connor Grey series has this as a backstory. Faerieland suffered some sort of calamity, so all The Fair Folk had to settle on Earth. Now they're coexisting uneasily with humans, and much magic is being done.
In Ben Aaronovitch's novel Rivers of London the Commissioner of the Metropolitan Police is disgusted but not totally shocked to learn that the Home Office projections were wrong and that the magic has indeed been coming back since about the mid-sixties.
In The Wheel of Time series, as it progresses, a number of magical Talents that were lost start reappearing. Even some abilities that never existed like Healing stilling have been discovered. This is only a partial example, because magic never went away entirely.
Partly straight, partly averted in The Dresden Files. In that world, the past was very much magical, most of the old fairy-tales and myths have at least some basis in reality, but that world evolved into ours, which superficially appears to be magic-free. Partly averted, in fact magic never went away, it's still quite common and very potent, but a Council of the most powerful Wizards deliberately worked to suppress the other magical nasties and police their own, giving the human race breathing space to expand, grow, and industrialize.
In The Grimnoir Chronicles, magic appears due to the arrival of some kind of Cosmic Being, which seeds people with magical power, lets it grow as they use it, and harvests it when they die.
This is happening slowly in the Kate Daniels universe. Tech is slowly losing to magic, which drives as a major driver for social and cultural change.
In The Stand, after a virus wipes out most of humanity, supernatural events start occurring with increasing frequency: everyone starts having psychic dreams, Randall Flagg goes from a vaguely mystical vagrant to a full-fledged Humanoid Abomination, and at least a few divine miracles occur. Magic and civilization are treated as opposing forces in the book; early, uncivilized peoples experienced magic more often, and, now that civilization's crumbling, magic is on the rebound.
In S. M. Stirling's Emberverse series it's a result of the Change that wipes out all tech above a medieval level. In the first trilogy, set during the first decade after the Change it's somewhat dubious but becomes quite explicit in later books set a quarter century after the Change. After Rudi acquires the Sword of the Lady it seems to takes another leap forward.
In Tim Lebbon's Dusk and Dawn, magic is coming back. This turns out to be a really bad thing.
Quantum Gravity‍'‍s humans believe this happened. The other races insist that they could and were sneaking into the human world to generally make mischief, it's just that they weren't being obvious about it before. It's a little difficult to tell which is true, since anyone who says such a thing just admitted they like messing with people.
Inverted in The Empire of the East trilogy by Fred Saberhagen, and, by extension, in his Books of Swords and Books of Lost Swords series, in which Technology Comes Back. All three series are set in the far future of earth, after the United States, as a last resort to avoid the destruction of the world in an imminent (as in the missiles were being launched at that moment) nuclear war, activated a device designed to alter the laws of physics within the vicinity of the planet so as to make nuclear fission so unlikely that the chain reactions which power nuclear bombs became impossible. It worked a little too well, as changing the laws of nature also caused almost all advanced technology to cease functioning, causing the collapse of technological civilization, and also unleashed the powers of magic, causing the rise of a civilization based on magic. At the end of the Empire trilogy, however, the Great Change was partially reversed, allowing advanced technology to function once again. The magic, however, does not go away.
In The Riddle-Master of Hed, the world itself was always deeply magical and this never changed, but actual wizards had vanished centuries ago. They return during the course of the trilogy, and the most powerful, Ghisteslwchlohm, never went anywhere — he just hid his true identity to impersonate the High One.

Tabletop Games

In the Rifts campaign setting, the simultaneous deaths of billions of humans in an apocalyptic ~~war~~ accident caused a magical chain reaction that re-energized Earth's ley lines and opened up rifts from all corners of the multiverse.
In the Shadowrun campaign setting, magic returns after centuries of dormancy, which causes elves and dwarves to be born of human parents as well as causing others to change into orcs and trolls.
In the Deadlands campaign setting, magic returns when a Sealed Evil Legion In A Can is released, leading to such things as walking dead, mad scientists, and all sorts of inhuman monsters.
When the dimension Alara from the Magic: The Gathering multiverse was broken into five pieces, each piece could only access three of the five forms of magic, with no two pieces accessing the same three forms of magic. Much of the story deals with the five shards of Alara coming together, and the huge problems the reemergence of unknown forms of magic and the mindsets behind its practitioners are causing it.
In the Alternity campaign setting Dark•Matter, the level of supernatural activity on Earth is directly linked to the amount of dark matter in the universe, which is likened to a tide pool. The rising tide of dark matter, however, is not a good thing. Not only are many supernatural beings extremely dangerous, but previous risings of the tide have resulted in mass extinction events, as noted in the Mayan calendar.
- This idea was later copied for Urban Arcana, a D20 Modern campaign setting. Here, the tide is actually the Shadow Plane and the supernatural forces are the monsters of Dungeons & Dragons. There's no Apocalypse looming ahead, though.
In the GURPS setting Technomancer, the Trinity nuclear bomb tests and Oppenheimer's famous words, "I am become death, the destroyer of words" (in reality, he only thought of them at the time) completes an ancient ritual and returns magic to the world, which humanity promptly fuses with technology to produce all kinds of strange ramifications.
RPGA's Living Death campaign managed combines this with The Magic Goes Away. The campaign ended with the heroes (assuming they don't fail the final adventure) successfully banishing the Red Death from Earth. Since the Red Death had hijacked all magic on Earth millennia ago (which forced all users to make a check or be corrupted when casting), all magically powered creatures die instantly during the finale, but it allows normal magic, uncorrupted by the Red Death, to return.

Video Games

Happens in the backstory in the MMORPG City of Heroes: Two friends discovered Pandora's Box, and upon opening it, unleashed the "total sum of human achievement" upon the entire world in one day, not only bringing back magic, but allowing humanity to make sudden leaps in science and technology, as well. The immediate and ongoing result is a world full of super-powered people!
Bringing magic back is your goal in Zork: Grand Inquisitor. It has already started to return before you get involved, as evidenced by Dalboz's journal entries and your working spellbook, but you still need to reunite the MacGuffins to complete the process.
Part of the Backstory for Guilty Gear. Gear Technology and their subsequent rampage brings about both Armageddon and the reintroduction of Functional Magic to society.
Final Fantasy VI begins with a narration stating how the War of the Magi devastated the world and brought about the end of magic... but in truth, the magic wasn't gone, it was merely sealed away. Now a power hungry Empire has rediscovered it and is using it as a weapon of conquest. It doesn't last long, however. In the end, upon the destruction of the Three Goddesses of Magic, The Magic Goes Away again, this time permanently.
In the first Shin Megami Tensei, the Demon Mother Echidna explains to the Hero how all manner of supernatural creatures roamed freely across the primitive Earth... until "the Hebrew God" conquered them and cast them down into darkness to rule alone. Of course, humans are incapable of using magic, only so-called "demons" can, and so the rule of God went unopposed for millennia. After the End of our world, Twenty Minutes Into the Future due to nuclear annihilation, Gaia's children have returned and brought magic back with them, and they're not going to give up so easily this time.
Lionheart: Legacy of the Crusader is all about this trope. About ten thousand years ago a spell was cast to eliminate all magic and fantastic beasts. Then during the crusades of Richard the Lionhearted a counterspell was cast (somehow, no magic remember?) after the execution of 3000 arab prisoners, releasing all manner of nasties into the world.
Golden Sun revolves around a deliberate attempt to bring back the magic, with the first game following those who think magic is too dangerous to restore, and the second following those who think it must be brought back. The heroes of the second game are right. Magic was a basic part of nature, and without its influence rising tides are slowly submerging the land. In addition, magic was the foundation of most of the technology in the setting, and without it, technology stagnated--as one character observes, no extant civilization has built or could build anything as impressive as the ancient ruins you spend most of the series trekking through.
- However, this has had major repercussions, as the world looks like it's heading to an even earlier end with the Big Bad having attained god-like powers, and the whole world having descended into warring nations.
The goal of the Big Bad in The Longest Journey could be considered this, in that he plans to re-join the worlds of Stark (world of science, i.e. our Earth) and Arcadia (medieval world of magic), which have been split up for millennia due to the dangers of mixing science and magic. In the beginning of the game, strange, magical things start happening to the people of Stark. Also, the fact that all advanced technology failed in-between The Longest Journey and Dreamfall implies that it was an unwitting product of magic seeping into Stark.
The starting point of the plot in the little known Spellcraft - Aspects of Valor.
Darkly deconstructed in NieR. The magic introduced into the world via Caim, Angelus and the Mother Grotesquerie crossing over from the Drakengard universe literally causes The End of the World as We Know It. The result is the incurable White Chlorination Syndrome and The Legion. By the time the game actually starts, humanity as we know it is entirely extinct.
The page quote from Dragon Age II is from a world where Functional Magic is widely acknowledged (and feared for various reasons up to Beware the Superman and Demonic Possession) and seems quite out of context, except that the person in question can do things other dwarves can't, as Dwarves are the only known race in the setting that can't produce mages. (As of the end of Dragon Age II, we're still not sure exactly what Sandal does when he slaughters hordes of Darkspawn and demons), other than it being "Enchantment!" or rarely "Not Enchantment!" (Note that enchantment in this setting is inscribing runes to be used on weapons and armor which Sandal excels at and enjoys doing.) There are also hints that the history of his people (and of humans and elves as well) is incorrect on some level, leading to much Wild Mass Guessing about what Sandal means.

Web Comics

The basis of the furry web comic Code Name: Hunter. In a subversion, there are places where the magic was never sealed away, such as Australia.
Fantasy races are rediscovered in Corner Alley 13.
Yosh! had in it's backstory the world suddenly re-gaining a large amount of magic and people changing into semihuman forms when the first of 5 seals keeping magic away from the world is broken. When the second seal is broken, more magic returns, magical creatures reappear, and a sunken island rises - into the sky.
In The Phoenix Requiem, magic was provided by the spirits, who were imprisoned 700 years ago. They seem to be coming back. The catch: it is revealed that they are the bad guys.
This might be Pandora's goal in El Goonish Shive.

Web Original

The ramifications of this is an ongoing theme in The Descendants, where the return of Western style magic (Eastern magic seems to have survived) is allowing monsters from Faerie to cross over and people with natural powers to manifest. Interestingly, magic seems to have died from disuse rather than being sealed away.

Western Animation

This was the premise of the 1980's animated series Visionaries: Knights of the Magical Light.
Making the people of Earth believe in magic again is part of the mission the Winx Club has in season 4.
While never stated directly in the show, Word of God says that Adventure Time takes place on our Earth, after some disaster wiped out humanity and magic returned to the world. It's unclear if the show will directly address it in the future.