The moment every man, woman, and child climbs on to their beds, rest their heads on a pillow, and close their eyes before drifting into sleep for the night, something evil begins to stir. When you would normally expect to find yourself riding a unicorn in a colorful land made out of candy and pastries, or relishing in your complete freedom as you soar the cosmos as Superman, you'll instead find yourself in a dark, horrifying parody of a dream that specifically seeks to drag you into a pit of despair. You'll find yourself in a haunted forest stalked by creepy dolls with knives, drowning in a lake of thick, black oil, forced to run naked with legs made of Jello as the teleporting Monster Clown inevitably grabs you and vomits flesh eating maggots all over your face... Or dropping your ice cream on the floor.
As it turns out, there's an entity responsible for those horrible, sleepless nights, in the same way The Sandman is thought to bring good dreams.
Meet the Nightmare Weaver, a Sub-Trope of Dream Weaver who exists for the sole purpose of making people wear brown pants in their beds with his bad dreams, and he most likely enjoys doing it. Chances are, he may know just about every fear or guilt he can use to psychologically torture you, and when he's feeling particularly nosy, he'll walk up to you in your sleep and corrupt whatever happy dream you were having at the moment with a simple touch of the finger. If he's feeling lazy, he can send stab-happy dolls, teleporting maggot-vomiting clowns, teleporting doll clowns that vomit maggots with knives, and a plethora of other foul apparitions to do the dirty work for him. More often than not, he'll be not just any boogeyman, but the Boogeyman, maybe even the very incarnation of nightmares with his own personal Mordor of night terrors, and he's nearly always present in settings revolving around Dreams vs. Nightmares, clashing with the do-gooders trying to keep it all sugary sweet. Expect him to aspire to Take Over the World with his nightmares, and be portrayed as Always Chaotic Evil.
In short, this kind of character is Exactly What It Says on the Tin; a Decomposite Character deriving from The Sandman who embodies the latter's negative aspects in some portrayals. Particularly cruel ones like to pull you into Your Worst Nightmare, as well as alcohol poisoning to those who take a shot every time the word "nightmare" is mentioned in this article.
In Fantasy Kitchen Sink type settings, this entity will usually be portrayed as among the evilest and most dangerous entities out there, despite the fact that nightmares, by their nature as dreams, have almost no capability of causing any real or lasting harm to a person.
- Nightmare in the Marvel Universe (originally and most commonly an enemy of Doctor Strange, but he's encountered a lot of other Marvel heroes) is the evil nightmare-creating ruler of a "Dream Dimension".
- Morpheus from The Sandman is a rare heroic example; as the lord of ALL dreams, he also creates nightmares, usually as a way to reflect mankind's darker aspects.
- In the Jingaroo comic series in Beckett Pokemon Collector, the villain Croco-Vile had power over dreams and nightmares and was known as the Nightmare King.
- Dr. Destiny, an enemy of the Justice League of America, has this has his shtick. Early on, he used a machine called the Materioptikon, which was powered by Morpheus's dreamstone. When he and a weakened Morpheus fought over the Dreamstone, they used nightmares (though Morpheus was rather better at it, forcing Destiny to resort to less subtle measures).
- Wonder Woman (1987): Circe imposes nightmares about Hippolyta's then very recent death and Vanessa being kidnapped and transformed into the new Silver Swan on Diana and Donna. It takes them about a week to realize their bad dreams are being inflicted on them rather than just being caused by everything that happened recently.
- Child of the Storm: Morpheus, as per canon - it's one of his many roles, given that he is, after all, Dream. He uses it both benevolently (forbidding his nightmares from Harry's dreams, after the events of Forever Red - though Harry has nightmares anyway, because the memories are bad enough), and, well, malevolently, as Yelena Belova found out. The full details aren't made clear, but it warped her body, put her in a strait-jacket, and was so bad that even a vengeful Loki couldn't think of anything to add.
- A Diplomatic Visit: The Lord or Lady of Nightmares, a Power and the Opposite of the Lord or Lady of Dreams, is explained to have the Duty of creating and giving bad dreams to those who have fallen down a dark path in order to scare them back into behaving.
- In Rise of the Guardians, Pitch Black, who appears in the illustrative image above, is the evil counterpart of Sandy, who gives bad dreams to children with his black sand and has a legion of horse-like monsters at his disposal.
- Freddy Krueger from A Nightmare on Elm Street, who was inspired by the Gary Wright song "Dream Weaver." The dreams Freddy creates are nightmares that can kill you, with any damage done in the dream crossing over into the real world. The only way to escape the nightmare is to wake up. However, Freddy often traps his victims in a Dream Within a Dream, so even if you think you escaped him, you might not have.
- Twice Upon a Time revolves around a plot by Synonamess Botch, the head of the Murkworks (the land of bad dreams) to trick two citizens from Frivoli (the land of pleasant dreams) to helping him bring about endless nightmares for the folks in the Land of Din (our world).
- In A Journey to the Land of Dreams by Dmitry Drimov, the Big Bad rules over nightmares and drug-induced hallucinations, but interestingly, he is aware that his domain isn't very pleasant. His planned solution (summed up roughly) is to steal all the colors from the Land of Dreams to make the nightmares prettier.
- Bruce Coville's Book of... Nightmares: Weztix, the Lord of Nightmares in There's Nothing Under the Bed, weaves bad dreams and transfers them into the head of one of his delivery boys, who then rises up underneath someone's bed and whispers the contents of the nightmare to the sleeper.
- The titular character of the story "The Nightmare Man" in The Sarah Jane Adventures is an entity of unknown origin who traps people in endless nightmares.
- Dungeons & Dragons:
- Night hags are an Always Chaotic Evil Witch Species who intangibly visit sleepers and "ride" them with horrific nightmares, which slowly kill the target. According to some sources, those who die from a Night Hag's nightmares have their souls trapped and bartered to demons.
- Dream larvae are Semi-Divine abominations who can not only inflict nightmares at will but physically absorb victims into deadly, sanity-destroying dreams. In the waking world, they manifest as the viewer's worst nightmare to scare them to death.
- Forgotten Realms: The bite of Dendar the Night Serpent causes her victims to fall into a sleep haunted by a continuous stream of nightmares, her dislodged scales turn into nightmares that burrow into the mind of the closest living being, and she can force any being anywhere to instantly relive the worst nightmare they ever had.
- In Nomine: Beleth is the Demon Princess of Nightmares. She sends nightmares to inflict terror and horror on sleeping people to push them toward their dark fate (ending up in Hell).
- Magic: The Gathering: Ashiok the Nightmare Weaver is a Humanoid Abomination who draws power from fear, can manifest people's darkest nightmares in reality, and is attempting to birth a new god from the distilled nightmares of an entire Plane. Formerly human, Ashiok is transforming piece py piece into the stuff of nightmare itself with every victim they claim.
- Nightmare from Kirby's Adventure is, as the name implies, a demon who exists to cause nightmares. King Dedede trapped him inside the Fountain of Dreams and destroyed its key, the Star Rod, to stop him from terrorizing Dream Land.
- In Klonoa, the evil Ghadius in Door to Phantomile plots to destroy the titular land by summoning Nahatomb, an Eldritch Abomination literally made from nightmares.
Ghadius: Hear this, strange dream! The world is finished! And this is the beginning of the perfect nightmare!
- NiGHTS into Dreams...: Wizeman the Wicked is a powerful, god-like being who serves as creator and leader of the Nightmaren, the creatures you see in nightmares. He aims to corrupt Nightopia, the land of good dreams, and Take Over the World.
- Darkrai fills this role in the Pokémon series, capable of trapping anyone in a neverending nightmare, not that it really wants to. For this reason, it usually hides itself away from other living beings and/or stays relatively close to its counterpart Cresselia, whose feathers can free its victims. In addition, any Pokémon with a Ghost-type attack can use a move called Never-Ending Nightmare if it's holding a Ghostium-Z Crystal.
- The Elder Scrolls:
- Nightmares fall under the domain of the Daedric Prince Vaermina, who not only causes them to happen to mortals by merit of her mere existence, she utterly delights in tormenting mortals with them. It is also thought that she genuinely believes the nightmares are gifts, despite the fact that they can and sometimes do end up Mind Rape -ing the poor mortals she chooses to torment. Not that she would care, of course.
- A more specific example would be her Daedric Quest in Skyrim, where the Dragonborn teams up with a priest of Mara, who also happens to be a former servant of Vaermina, to destroy her Daedric Artifact the Skull of Corruption, which had been stealing the dreams and memories of the nearby townsfolk and tormenting them with horrific nightmares.
- One of the lesser antagonists of World of Warcraft is Xavius, a saytr who created a world called the Emerald Nightmare and is fittingly known as "The Nightmare Lord".
- Althea the Nightmare, from Farnham Fables, is a very downplayed example, despite her scary title: she's a Dream Walker who enjoys tormenting people in their sleep, but her idea of "torment" is closer to mild mischief than actual nightmares: in Episode 4, all she really does is hide Rainbow Keys around Theresa's dream and make her find them.
- Sackboy: A Big Adventure: Vex is the Lord of Nightmares. He spends the game trying to build the Topsy Turver, a machine that will let him spread fear and chaos.
- In Blackout's backstory, he was born in the Realm of Dreams and recruited into a clan called the Dark Stygian. They combined this trope with Scare 'Em Straight, as they would use their powers to dishearten evildoers by tormenting them with nightmares. However, they eventually fell Drunk on the Dark Side, and began to abuse their powers and spread bad dreams far and wide For the Evulz. Blackout, however, was having none of it and defected, leading to Master Eon eventually recruiting him into the Skylanders when he was threatened by said nightmares and saw Blackout fight them.
- Champions of Far'aus: Hypnoron gives Daryl & Skye nightmares in story #4, and in story #6, Sweet dre - NIGHTMARE, pulls Karla, and the rest of the group out of their own dreams into his nightmare dreamscape, where he quickly splits them up, putting Daryl, Skye, and Flamel in personalized nightmares that Karla has to help them out of, with an additional nightmare monster chasing them down as they try to leave.
- Poet Anderson The Dreamwalker has the villainous REM, known as the bringer of nightmares for the people in dreamland.
- Zordrak from The Dreamstone is the Evil Overlord of Viltheed, the Mordor of the Land of Dreams. The show revolves around his attempts to obtain the Dreamstone, which spreads dreams around the world, so he can send out nightmares (although later episodes add in that getting the Dreamstone will also let him Take Over the World, to raise the stakes.)
- Him does this to The Powerpuff Girls in "Power-noia," invoking each's worst fears in nightmare form. Blossom's is failing in school, Buttercup's is her fear of spiders, and Bubbles' is being attacked by her stuffed toys. When Blossom suddenly realizes Him is behind it, she puts on her game face and proceeds to make things right again.
- Hilda has The Marra, a group of Ambiguously Human teenage girls that can give people nightmares, which they later share with other Marra and feed on the negative energy caused by said nightmares.