Ominous Fog

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"To one who, journeying through night and fog,

Is mired neck-deep in an unwholesome bog,

Experience, like the rising of the dawn,

Reveals the path that he should not have gone."

- Joel Frad Bink

Fog can be just part of the ominous general mood or inseparably tied to a dangerous and creepy supernatural phenomenon. This is only about the ominous mood it creates:

Maybe it is the way you feel alone in the fog, even with your companion next to you. Maybe it is how the fog seems to swallow everything and makes noise and sight unfamiliar. Maybe it is the way it curls and sways around you, as if it knows you are there. Maybe it is the fact that a monster could lurk a few meters from you and you wouldn't know it.

If the environment is empathic, it should be possible to read your general situation from the weather. Now, everyone with even a whiff of genre-savviness knows, that dense fog is about as bad a sign as a howling tornado on the horizon. Is sometimes accompanied by a blood red sky.

Anime and Manga

 * Fog also appears when the Big Damn Heroes reach the center of Shinjuku in Demon City Shinjuku.
 * Digimon Tamers gives us the pink "Digital Field", where many of the early fights take place. In the original Digimon Adventure, Myotismon creates an Ominous Fog that cuts Odaiba off from the rest of the world.
 * The geography of One Piece gives us the Florian Triangle, an area of ocean covered in Ominous Fog where the number of ships which have vanished is well in the hundreds if not higher. Within it is the Thriller Bark, the gargantuan ship Gecko Moria uses as his base. The trope is slightly inverted in that the fog is actually protecting the victims of Moria, who cannot be exposed to sunlight after he steals their shadows. It's played straight at the end of the arc, which implies that there is indeed something within the fog besides the Thriller Bark that attacks ships.
 * Science Ninja Team Gatchaman: In an early episode, clouds of Ominous Fog cover an oceanic area where ships are vanishing. At the beginning of the episode a character tells he does not like that eerie fog and it is crepping him out, and another character scoffs that are silly superstitions and there is nothing to be frightened of... right before they disappear.
 * Magical Pokaan has a vampire robot that creates its own fog.

Comic Books

 * Storm from X-Men is a weather manipulator who not only can summon fog at will, but the weather is the Empathic Environment, responding to her moods. Fog does not usually bode well.
 * From Hell

Film

 * King Kong: In all three versions of the story, the approach to Skull Island is shrouded in fog.
 * Pirates of the Caribbean: One of the features of the Aztec curse seems to be a perpetual fog that follows the Black Pearl around.
 * Most Jack the Ripper films.
 * A sudden fog that comes right out of nowhere (and disappears just as quickly) appears during Mother Gothel's Dark Reprise in Tangled.
 * In Dagon everything is fine until the fog and rain start rolling in.

Folk Lore

 * Kuchisake-onna is said to roam especially during ominously foggy evenings, looking for helpless victims.

Literature

 * A Wizard of Earthsea. Duny (who later becomes Sparrowhawk) uses a fog control/illusion spell to confuse invaders and save his village.
 * Brandon Sanderson's Mistborn trilogy features metal-burning magic-users who have a certain affinity with the concealing mists that form from nowhere at nightfall, which commoners fear.
 * The Mist. Even when the monsters are not attacking, the ever-present fog strongly emphasizes the isolation of the survivors, and the alien nature of the world outside.
 * Gone with the Wind. After suffering hunger and cold during the Reconstruction, Scarlett has a recurring dream of running through a mist. The dream comes true after Melanie's death, when Scarlett runs home to her mansion in the hopes of reconciling with Rhett. Rhett winds up leaving her. Ominous, indeed.
 * In the Old Kingdom trilogy, fog can be a cover for Dead, for whom light is dangerous.
 * The Tales from Camp Crystal Lake series of books by Eric Morse all feature a yellow fog which seems to make everyone feel more negatively, lubricating the lethal intentions of whomever finds the hockey mask as well as the Final Girl.
 * In Robert E. Howard's Conan the Barbarian novel The Hour of the Dragon, Valerius curses the fog until he realizes it would hide his advance.

Live Action TV

 * The X-Files. In "The Ghosts Who Stole Christmas" Scully wryly notes the presence of onimous fog outside a creepy old house and (correctly) guesses that it must be haunted.
 * Justified in the Stargate Atlantis episode "Whispers", in which the monsters create the fog as a predatory mechanism.
 * Star Trek: The Original Series episode "Catspaw". The fog is weird because as Spock points out there is no water anywhere in the region.

Professional Wrestling

 * Besides the darkness and the awesome creepy music, The Undertaker, in Deadman form, also has a good deal of fog covering the entrance way as part of his Nightmare Fuel-inducing entrance.

Tabletop Games
"One word: Fog"
 * In the Tabletop RPG Deadlands, this ability is available to the Harrowed, particularly those who were ominous in life, or closely tied to nature. It has little, if any, effect on game mechanics. But boy, is it creepy!
 * Lampshaded in the Dungeons and Dragons supplement Heroes of Horror at the end of a list of ways to turn up the paranoia factor. Also, Ravenloft.


 * Dungeons and Dragons Eberron setting also gives us the Mournland, which is an (ex-)country made of this trope.

Theater

 * The Benjamin Britten operas Peter Grimes and Billy Budd have scenes with Ominous Fog.
 * In Macbeth, the witches chant, "Fair is foul, and foul is fair. Hover through the fog and filthy air." (Also, the witches live on a moor, and Scottish moors are prone to fog.)
 * In Hamlet, the old king's ghost first appears on a foggy night. Which makes sense since they're in Denmark and the castle is probably pretty close to the sea.

Toys

 * The swamps of Karda Nui in Bionicle are shrouded in fog- it's so thick that it can't be seen through even with X-Ray Vision. During the Visorak invasion, a thick green mist blocking out the sunlight is also mentioned.

Video Games

 * The Legend of Zelda Phantom Hourglass. The fog only occurs around the ghost ship.
 * Silent Hill, with fog originally added to hide the graphical limitations of the Playstation, is one of the more obvious examples, and eventually grew up to become one of the central parts of the atmosphere; in fact, Silent Hill 2 for PC would never run on a GeForce 4 MX card, because the fog was just so goddamn detailed. Makes the gameplay bad and scary, shows that the setting is bad and scary, and is also caused by the town's bad scaryness. Among videogames it's infamous enough to be a Crowning Fogof Aweome Bad Scariness
 * Pokémon Diamond and Pearl introduced the fog atmosphere--it lowered your accuracy in battle. The HM Defog could get rid of it, but with a bit of trial and error it's possible to find your way through without the practically useless move. The first Pokemon game to use this trope was R/S/E, in Mt Pyre
 * Sand of Neverwinter Nights 2, upon seeing one of these, declares: "I suppose this is the 'impending' part of our impending doom."
 * In Fire Emblem, sometimes the mountain-based stages are covered in fog that drastically reduces your party's chance to freely go through *and* hides enemies from you. You either bring a Thief into the party, get some Torches, or use the Torch staff to solve the problem.
 * In Persona 4, murders occur when the fog is heaviest. In the latter parts of the game, it never goes away. The game is centered around finding the truth in the fog, which means finding the true culprit and bringing them to justice (although if you look deep into the game's philosophy and symbolism, it's a lot more than that). Also, the fog
 * Indie PC horror game The Path features ominous fog when you get near the lake in the woods.
 * Touhou 6: Embodiment of Scarlet Devil's very plot involves red fog clouding the sun. Though it doesn't show up on your screen.
 * Prince of Persia: Warrior Within. There is a foggy area filled with many enemies the player must pass through before reaching the final boss.
 * In ~Demon's Souls~, an ominous fog is what caused Boletaria to be overrun with monsters. In-game, harder sections of the dungeons are marked by walls of fog. If you see one in a large passageway, a Boss Battle awaits you on the other side.
 * The fog sectioning off the game world also applies to its Spiritual Successor Dark Souls.
 * In New Super Mario Bros Wii, there's an ominous dark purple advancing wall of Ominous Fog moving forwards through level 8-1, which One-Hit Kill any player characters (and maybe enemies) on impact. Best advice is obviously to run.
 * In Alan Wake, you spend most of the game running through (natural) fog shrouded forests. Every so often though, the wind will pick up and the fog turns pitch black. From a story perspective, it indicates the Dark Presence is nearby, while from a gameplay perspective it indicates that you're about to be swamped by the Taken. Both are pretty effective at upping the tension.
 * Echo Night: Beyond featured fog that made the ghosts you were trying to help very hostile, forcing you to try and find ways to avoid or clear it out.
 * In Alice: Madness Returns, there is an Ominous Fog in the Hyde Park sequence. To get out the player must follow the lamps, and besides their light there is nothing but the fog and the darkness.

Web Comics

 * Derelict Engulfing her boat
 * Roza Whilet chasing a thief
 * Thistil Mistil Kistil: a misty fjord

Web Original

 * A common element in The Slender Man Mythos; it's very common for a foggy picture of trees to have just one tree, just one that looks a bit off. Then you see a man-shaped object among the branches.

Western Animation

 * Avatar: The Last Airbender: Katara can whistle up fog at a moment's notice, for cover or spooky effects. Fog rolling in inland is ominous to those who don't know a waterbender's about. Also parodied in a dream Aang had: he makes a dramatic entrance by kicking in the door, snaps his fingers, and fog rolls in.
 * The Simpsons parodies Ominous Fog in the Treehouse of Horror short featuring werewolf Flanders. "Guess I forgot to put the fog lights in!" Also, the other Treehouse Of Horror short with the fog that turned people inside out featured Ominous Fog.
 * Justified in the Scooby-Doo, Where Are You? episode "Go Away, Ghost Ship," in that the mysterious fog that always accompanies the "ghostly" Redbeard's pirate ship is produced by dumping blocks of dry ice into the water.