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[[caption-width-right:300:A fresco of the rite of the goddess Isis found in Herculaneum]]
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Popular in ancient Greece and Rome, Mystery Cults are ultra-exclusive "clubs" that require total secrecy on the part of participants and may tell new members little or nothing about their ethos before they join, and often long after. Generally speaking only long-time members will know what the cult is actually about, and even then the "Inner Circle" will be the only ones who know everything.

In this respect they are the opposite of religions such as Christianity, Islam, and Buddhism, which are more evangelistic and make materials relating to their beliefs freely available and are happy to explain what they believe. Indeed, because such religions view their beliefs as having the potential to transform someone's life and save them, they typically consider it sinful to ''not'' be willing to share it.

To an ingroup, secrecy can feel sacred, respectful, and powerful. To an outgroup, though, secrecy often feels sketchy. What do these people have to hide?

The word "cult" is an example of HaveAGayOldTime. In modern English, "cult" is a term used to describe groups perceived as being deviant, fringe, or illegitimate. In an ancient context, however, "cult" simply refers to veneration.[[labelnote:etymology]]The Latin word "cultus" is related to the English word "cultivate" and meant care, protection, nurture and -- metaphorically -- worship.[[/labelnote]] Thus, the "Cult of Apollo" just means the veneration of the god Apollo. When the details of that veneration are kept secret, it's a "mystery cult".

In fiction, this combination of secrecy being seen as sketchy and the misunderstanding the term "cult" often leads in to a really obvious ReligionOfEvil. The PathOfInspiration is a particular type of evil mystery cult which employs trappings of a benevolent religion to disguise itself. Compare and contrast AncientConspiracy. See also SecretCircleOfSecrets. A joke version is often a BrotherhoodOfFunnyHats.

'''Note''': As a general rule this trope only applies to things that are described as a cult, religion, or sect, etc, InUniverse or by WordOfGod.

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!!Examples:

[[foldercontrol]]

[[folder:Anime & Manga]]
* ''Manga/AttackOnTitan'': The "Wall Cult" believes that the huge, circular walls that protect the last of humanity were a gift from God, even yelling at people who touch or get near the walls. Eren notes that even just putting cannons on top of the walls took way longer than it should have because the government had to work around the cultists. Most of the members are simply religious people, but the inner circle seems to know more about the walls than it seems, [[spoiler:including that there are Titans within them]].
* ''Literature/UnlimitedFafnir'': A dragon cult exists, which has been brainwashing Tear and causing her to believe she's really a dragon, not a human. Having horns on her head only further validates it as far as she knows. The main characters attempt to un-brainwash her, by having her live as a human. Unfortunately the cult leader, also a human, has instead chosen to live the life of a "dragon", hurting and killing people using their powers, much like the real dragons that showed up 25 years before the current events in the show.
[[/folder]]

[[folder:Comic Book]]
* ''ComicBook/HackSlash'': The Society of the Black Lamp began as a mystery cult founded by Akakios of Panopolis--the world's first Slasher--in ancient Greece.
* ''ComicBook/{{Providence}}'' reimagines Lovecraft's Church of Starry Wisdom as a mystery cult called the Order of Stella Sapiente. Boggs and Wheatley complain about the main leaders not listening to all the suggestions of its members because the former two are despised by the more snobby figures in charge. The leaders which includes Ephraim Wade have their own plans with the Booke of the Wisdom of the Star and ensure that the knowledge is kept out of reach of the Wheatleys and others.
[[/folder]]

[[folder:Film -- Live Action]]
* ''Film/TheFactsInTheCaseOfMisterHollow'': {{Implied|Trope}} -- an unseen investigator researches "paganism" revolving around a secret Greco-Roman religion, with its practitioners having spread as far as northern Ontario, where they're suspected in the disappearances of over one-hundred children.
[[/folder]]

[[folder:Literature]]
* ''Franchise/CthulhuMythos'': Creator/HPLovecraft was fond of including these in his horror stories, most famously the Cthulhu cultists and the townsfolk in Innsmouth.
* Creator/NgaioMarsh's ''Literature/DeathInEctasy'' features a cult in the mid 1930s. The murder victim is poisoned in the special beverage she drinks during a ritual. Naturally, the investigation is hampered a bit by the secrecy of the cult members.
* The real-life cult of Mithras has featured in several historical novels, among them Creator/RosemarySutcliff's ''Literature/TheEagleOfTheNinth'' and Creator/JohnMFord's ''Literature/TheDragonWaiting'', which each have a protagonist who's a member.
* ''Literature/{{Elantris}}'': The aptly-named Mysteries is an enigmatic cult with a very unpleasant (and largely deserved) reputation. Turns out that it's a corrupted knockoff of the peaceful Jesker religion, but where Jesker is dedicated to living in harmony with the Dor, the Mysteries is just about hacking into it to gain supernatural powers. [[spoiler: King Iadon of Arelon is a follower of the Mysteries, and when he's caught in the middle of sacrificing a servant as part of a ritual, his already-shaky reign outright collapses.]]
* ''Literature/TheGoldenAss'' ends with the main character restored to human form by the goddess Isis and entering her cult. He undergoes a number of initiations into deeper mysteries, each costing more money than the last.
* ''Literature/ImperialRadch'': The Radchaai GalacticSuperpower's state religion embraces syncretism to make it easier for conquered peoples to assimilate. Mystery cults are allowed, but are required to make the [[ImmortalRuler Lord of the Radch]] a member with full access to all their secrets.
* ''Literature/SkulduggeryPleasant'' features so many that they might as well be the entire premise... and in fact may be. Villains in Literature/SkulduggeryPleasant books are almost invariably part of some evil cult bent on destroying the world or killing everyone in it. It's getting so it feels like that is the only possible motivation, out side of maybe revenge, which exists in this series.
* ''Literature/PuckOfPooksHill'': The Cult of Mithras is depicted as analogous to the Freemasons, to whom author Creator/RudyardKipling belonged.
* ''Literature/ASongOfIceAndFire'': The Free City of Norvos is [[TheTheocracy ruled by]] the Bearded Priests, a religion so secretive that no one outside the Priests themselves knows anything about its practices -- not even the ''name'' of the god they worship.
* ''Literature/TheWarlordChronicles'' feature two mystery cults. Mithraism (see below) and a cult devoted to Isis lead by Guinevere. Everyone involved treats them with immense reverence and fear, but to the reader it quickly becomes apparent that Mithraism is basically a veteran's drinking club, and the worship of Isis is a SexCult.
[[/folder]]

[[folder:Live Action TV]]
* ''Series/{{Battlestar Galactica|2003}}'': Mithras apparently has an analog in the Twelve Colonies of Man, but given that they're referred to as "Mithrasaries" it's possible they're not as secretive as the followers of Mithras on Earth. Apparently, old-school religious Gemenon considers them something of a protected minority.
* ''Series/{{Caprica}}'': Monotheism is illegal on Caprica and thus secretive by necessity.
* ''Series/DoctorWho'': The Silence is portrayed as a Mystery Religion dedicated to stopping the asking of a Question -- though really it is more of a SinglePreceptReligion than anything. Much later it's revealed to be a RenegadeSplinterFaction of the Papal Mainframe, a far-future Catholicish-Anglicanish mainstream religion.
* ''Series/TheGoodies'': Druidism is portrayed this way in "Wacky Wales". Strictly PlayedForLaughs, of course. (But, then again, perhaps it's ''rugby'' that's the mystery cult.)
[[/folder]]

[[folder:Music]]
* This is absolutely literally interpreted on the Music/BlueOysterCult's concept LP ''Music/{{Imaginos}}'', where part of the story-arc involves The Blue Öyster Cult, a shadowy mystical order who live beneath (and besides) a bay, and worship Les Invisibles.[[note]]God-like entities who manipulate the fortunes of Earth[[/note]]. The cover of the earlier album ''Music/FireOfUnknownOrigin'' provides a visual impression of what the acolytes of the Blue Öyster Cult might actually look and dress like.
[[/folder]]

[[folder:Religion & Mythology]]
* Greco-Roman mystery cults were a range of religious groups where participation was reserved to initiates.
** [[http://en.wikipedia.org/wiki/Mithraic_mysteries The Mithraic Mysteries]] was a cult in Rome between the 1st and 4th centuries. Because of their [[ExactlyWhatItSaysOnTheTin mysterious nature]] we know almost nothing about them. We know they worshiped Mithra, and worshiped in meeting places called Mithraeum. They left behind statues and mosaics, but no writings. A popular myth rose up about hundred years ago in connection with the cult which says that Christianity was based on it, although it's highly unlikely -- Christianity seems to have started first.
** The best known example were the Eleusinian Mysteries, which is believed to have been a Demeter cult that had the story of Persephone at its center, as an explanation for the passing of seasons and possibly a cyclic nature of life.
** There are records of a cult of Isis in Ancient Greece.
** The Orphic Mysteries were a mystery cult with its own variation on the canon of Myth/ClassicalMythology, that focused primarily on chthonic (underworld) figures, named after Orpheus, the legendary bard who entered the Underworld to retrieve his wife. Its central deity seems to have been Dionysus-- specifically, the god Zagreus who was dismembered, eaten, and reborn as Dionysus (or something-their relationship is hard to pin down). They also apparently taught {{reincarnation}}.
** There is a serious scholarly debate about whether the [[http://en.wikipedia.org/wiki/Villa_of_the_Mysteries Villa of the Mysteries]] in Pompeii shows initiation into a Dionysian cult, or an allegory for marriage/a rite of passage. The rest of us just look at the pretty pictures. If the art is of an initiation, the process involves being whipped by a winged woman in thigh-high boots, which was probably some sort of symbolic punishment or purification.
* {{UsefulNotes/Mormonism}}'s relationship with this has evolved over time. In addition to churches (used for weekly meetings), Mormons also have temples (used for performing special rituals). One part of the temple ritual is that members vow not to reveal temple secrets. Traditionally, this meant that Mormons refrained from talking about what happened in the temple ''at all''. Eventually the church realized that NothingIsScarier; without information about what ''actually happens'' in the temple, people -- both non-Mormons and young Mormons who hadn't yet been initiated -- were imaging the worst and freaking themselves out. The church noticed that the ExactWords of the vow ''actually'' only stipulated secrecy around a ''couple'' details, not the ''entire'' ritual, so the church proceeded to publish a fair amount of information about the temple for a broad audience. Since across-the-board secrecy was the custom for so long, there's been some tension in Mormon communities as they adjust to the new openness and figure out where the new boundaries are.
* Scientology ranks its members according to their level of spiritual enlightenment, starting with Clear and then progressing through various "Operating Thetan" or "OT" levels. As members progress up the ranks (which--and even the Church does not deny this--usually costs money), they are said to be capable of handling more advanced Scientology teachings. The most famous of these advanced teachings is the Xenu story that leaked onto the Internet and has been parodied in various media. That's only OTIII; the later ones start to get weirder and increasingly esoteric.
* Within UsefulNotes/{{Native American|s}} religious practice, many ceremonies are "closed rituals". Generally, these ceremonies were not ''originally'' closed, but became such as a result of colonization. Native American religious practices were [[IllegalReligion legally banned]] for a time, forcing them underground. There have been anthologists who were interested, but not always respectful. Even when anthologists ''were'' doing their best, there's still an uncomfortable power dynamic in being a subject of study by someone else. There has been ForeignCultureFetish around the MagicalNativeAmerican. Eventually many tribes just said, "No more, we're done. No outsiders allowed in for this."
[[/folder]]

[[folder:Tabletop Games]]
* In ''TabletopGame/ArsMagica'', these are ''all over the place''. While Bonisagus tried to get away from the mystery-cult mentality when he created the Order of Hermes, mystery initiation is the easiest and most common way to gain unique magical abilities, particularly those that don't quite fit into Hermetic magic. Accordingly, four of the Houses and innumerable lesser groups are mystery cults, each dedicated to a unique heritage and practice of magic.
* ''TabletopGame/CallOfCthulhu'': The cults that worship the Franchise/CthulhuMythos deities are like this. They're intensely secretive because their abhorrent practices would get them imprisoned or executed in any civilized country. By the time a new member finds out what the cult is really up to they've probably been driven insane.
* ''TabletopGame/DungeonsAndDragons'': Most cults to evil gods and archfiends tend toward this in many good-aligned lands. It's when the evil god's cult becomes the state religion of a given land that open worship (with [[ReligionOfEvil all it entails]]) becomes a thing.
** One prominent variety of mystery cult presents itself to the world as a pastoral religion that offers freedom and catharsis and has rituals involving walking through mazes in animal masks. The hidden parts of the religion are its brutal predatory philosophy, rituals that involve HuntingTheMostDangerousGame (often initiates who got cold feet upon learning of their religion's true nature), and demon summoning. Only the highest echelons know their ''real'' deity -- Baphomet, the [[DemonLordsAndArchdevils Demon Prince]] of Beasts.
** Cults to Tharzidun tend to be ''multi-layered'' examples, as even the sort of people who will happily follow secret cults to evil deities and fiends [[EvilVersusOblivion tend to balk]] at serving the [[OmnicidalManiac god of omnicide]], so most of his cults are cults of something else that turns out to be another name for Tharzidun, with few if any worshippers knowing the truth. The Patient One and Elder Elemental Eye are common suspects.
** ''TabletopGame/ForgottenRealms'': Shar, one of the major deities, is usually worshiped by secret cults instead of large public temples, being the goddess of Darkness, Secrets, and Forgetfulness. And the colors of her priests are black and purple.
* ''TabletopGame/LeviathanTheTempest'' has this as an upgrade you can purchase for your cult that provides improved defense against investigation. Any investigation will first find the reasonable, sane people you've put in the outer layers, and unless they already know what they are looking for they are unlikely to dig further. The downside is that your outer-layer cultists ''are'' sane and lack the fanatical devotion of your Beloved, so there are a lot more limits on what you can demand of them before they walk away.
* ''TabletopGame/MageTheAwakening'' has a number of mystery cults, often used by the Awakened to guide [[{{Muggles}} Sleepers]] to true power. The Guardians of the Veil tend to use Labyrinths, hidden conspiracies that guide the worthy to enlightenment while shunting the unworthy off into temporal power, whereas the Silver Ladder tend to use Cryptopolies, political groups and secret societies that blend mundane influence with Awakened symbolism.
* ''TabletopGame/{{Nobilis}}'': Mystery cults are common enough that they're available as starting contacts on the lifepath system.
* ''TabletopGame/{{Paranoia}}'': The Secret Societies play with this trope to various degrees, with the Illuminati being the textbook example. Members know almost nothing about the group, and typically their only contact are random visits in the middle of the night by a single masked stranger delivering inexplicable orders. This being ''Paranoia'', it is entirely possible that the inner circle of any given society is just as completely clueless as the new recruits...
* ''TabletopGame/{{Pathfinder}}'': Cults dedicated to demigods tend to operate this way. While the faiths of true deities are widespread and operate in the open, those who revere [[CelestialParagonsAndArchangels empyreal lords]], DemonLordsAndArchdevils, the Eldest of the fey, the Great Old Ones and similar beings instead gather in secretive groups, practicing their rites in private locations and keeping the mysteries of their faiths hidden from outsiders.
* ''TabletopGame/PrincessTheHopeful:'' The most effective Dark Cults will often fall under this trope, keeping their true intentions hidden except from those already corrupted beyond recovery. C.O.R.D. (Community Organization to Reform Detroit) from the Ashes of the Motor City sample setting is a standout example: On the surface nothing more than a group of activists working to address race relations and class disparity in Detroit, [[spoiler: secretly RunningBothSides in order to promote racial strife and class warfare, push both sides past the MoralEventHorizon, and expand its own power.]]
* ''TabletopGame/RocketAge'': Venus has several Thuggee-esque murder cults that operate completely underground and are exclusive enough that the induction can kill you. Martian faiths have several sects that fall into this as well.
* ''TabletopGame/SystemsMalfunction'' features dozens of Mystery Cults of varying size and power, all engaging in one massive GambitPileup.
* ''TabletopGame/Warhammer40000'':
** Chaos cults often operate very covertly, and avoid being recognized for what they are through a combination of profound secrecy and of masquerading as more innocuous faiths. Since the alien and terrifying nature of Chaos typically scares off people who are confronted with its full brunt directly, cults often attract new members by pretending to be much more innocuous than they truly are, and later gradually expose them to more and more of the cult's true nature.
** Genestealer "cults" are the opposite due to their hive-minded nature, but their main ''modus operandi'' is to manipulate ''other'' cults which will fit the trope as a consequence.
** The Adeptus Mechanicus maintains a stranglehold on Imperial technology because many of its "mysteries" include the secrets to maintaining and operating the machinery that keeps the Imperium going. (Also, their Omnissiah may or may not be a sleeping EldritchAbomination, and it wouldn't really help their cause if that were to get out if it's true.)
** The Dark Angels chapter of Space Marines have a Mystery Cult as the foundation of their chapter teachings: recruits are taught parables that while not directly true have themes of loyalty, redemption through death, the need to keep secrets, and the perils of outsiders learning them. Some never learn the full truth; in particular the Ravenwing only educates those part of its Inner Circle of the Fallen, despite the company's purpose being to hunt down said Fallen.
* ''TabletopGame/WarhammerFantasy'': Both humans and elves are prone to forming these, with the Empire having multiple ones in each major city. Many turn out to be Chaos cults of one kind or another (and half of the rest usually belong to some other forbidden religion, like worship of Khaine or a Skaven spy operation), but some of them are genuinely just esoteric cults devoted to unusual aspects or worship of legitimate deities. Practically all cults to the TricksterGod Ranald are mystery cults operating from hidden shrines -- despite worship of Ranald not being forbidden or harmful in any way, he ''is'' the god of thieves, so his followers are understandably secretive.
[[/folder]]

[[folder:Video Games]]
* ''VideoGame/AssassinsCreedOdyssey'' features the Cult of Kosmos as the main antagonists of the game. Wearing masks to conceal their identities, and plotting the takeover of the entire Greek world during {{UsefulNotes/the Peloponnesian War}} by using an ancient Isu artifact and the PC's sibling as a brainwashed weapon.
* ''VideoGame/{{Bloodborne}}'': People outside the Healing Church generally only know that they worship Old Blood and practice Blood Ministration. Lower levels of the church know that their purpose is experimenting with the Old Blood, and the inner circle, known as the Choir, know that they're an offshoot of Byrgenwerth College dedicated to making use of the Old Blood to ascend themselves to Great One status, and they keep the existence of the Great Ones and all related things hidden from the general populace.
* ''VideoGame/CultistSimulator'': The cult the player starts is secret, as worship of the Hours is illegal.
* ''VideoGame/{{Diablo}}'': The Triune's new initiates were led to believe that they worshiped benevolent Spirits of Determination, Love and Creation, before gradually being initiated into the true teachings of the Triune and the true evil of the Prime Evils who the Spirits actually were.
* ''VideoGame/Doom2016'': Olivia Pierce's demon cult has multiple tiers of being an "Advocate" or employee of the UAC. The higher tier you are, the more involved you are not only in the inner workings of the corporation, but also in the cult that Pierce has gathered within.
* ''Franchise/TheElderScrolls'':
** Many Daedric cults are highly secretive and distrustful of outsiders, often because they fear being targeted by anti-Daedric vigilante organizations. In many regions of Tamriel, worship of certain Princes is outlawed, further driving these cults into secrecy. In particular, worshippers of Mehrunes Dagon, Molag Bal, Namira, and Vaermina are forced into hiding because their Princes demand something vile or unsavory of their servants.
** The Dark Brotherhood are followers of Sithis, and work as professional assassins. By their nature, they are an extremely secretive group, with their own hidden rites and initiations. The Morag Tong, their assassin rivals in Morrowind who worship Mephala, are the exact opposite, with the nature of their operations and practices being completely public in order for them to be sanctioned as a tool to regulate the Great Houses.
** It turns out that the ThievesGuild of Skyrim hides a mystery cult that worships Nocturnal and acts as guardians of her temple in exchange for good luck. Most of the thieves guild does not know this. Those who have been initiated into serving Nocturnal are known as Nightingales.
* ''VideoGame/DominionOfDarkness'': Some religions player can create -- like Cabal of the Undomitable Knowledge or Cult of Pleasure Seekers -- are secret. Others -- like Community of the Humble -- are more mainstream.
* ''VideoGame/TheSecretWorld'': The Morninglight (already distinctly reminiscent of Scientology) maintains a level of uplifting-but-vague ideology that serves to hide their true motives and methods from outsiders. As such, initiates have no idea what they've gotten themselves into, and little chance to resist once the MindRape starts. For good measure, any defectors are labelled "Obstructive Persons" and quietly eliminated.
[[/folder]]

[[folder:Webcomics]]
* ''Webcomic/AnEpicComic'': [[spoiler:Yje Society of the Free Mind's inner circle is only accessible if you become a free mind. The reason for this being is that you can't actually fully comprehend the true intentions if your mind is limited to the comic.]]
* ''Webcomic/GunnerkriggCourt'': The Court is openly an institution dedicated towards science, but most of the Court's real agenda is kept a secret from anyone outside their inner circles. The Court's inner circles do not openly advertise how to obtain membership, only inviting those who show their preferred mindsets, like a [[DoesNotLikeMagic healthy skepticism towards magic]]. The deeper into the Court's inner circles you make it, the shadier, more amoral, and downright creepy things get. [[spoiler:There are several reasons for this. One reason is because the Court is willing to resort to deeply immoral lengths to achieve their goals, and this policy helps keep their crimes hidden. Another reason is that the Court is in a paradox of DoesNotLikeMagic while also needing magic to achieve their goals, meaning that the Court's leadership secretly hates half of their own underlings. The biggest reason is because magic is shaped by ClapYourHandsIfYouBelieve. The Court wants to abandon Earth to create a new world, one completely under their control while being empty of the magic they hate so much. By limiting information about their project from the public, they hope to avoid letting their world be "contaminated" by more magic.]]
* ''Webcomic/{{Homestuck}}'': Parodied with the Clan of the Secret Wizard, a movement that forms around a salamander who found John's lost bedsheet, mistook it for a mystical artifact, dressed himself with it and took to the life of a wandering preacher. They're a secretive group that meets in hidden locations and haughtily keep their mysteries hidden from outsiders, but in practice their rites boil down to just "beholding" each other's robes, their practices mostly just ape the trappings of mystical religiosity, and rather than being exclusive they're so desperate for converts that they've taken to abducting strangers in the middle of the night and inducting them without knowing anything about their beliefs or moral character.
[[/folder]]

[[folder:Western Animation]]
* ''WesternAnimation/{{Futurama}}'': The League of Robots is a secret society of well-to-do wealthy robots (that somehow ends up having Bender as a member) that ostensibly exists to mastermind the robot dream of [[TurnedAgainstTheirMasters killing all humans]], but in actuality turns out to be more like a stagnant gentleman's social club.
[[/folder]]

[[folder:Real Life]]
* In general, any cult or religious organization that structures itself in this way can be considered an [[http://en.wikipedia.org/wiki/Esotericism esoteric]] body.
* The best-known modern example would be the UsefulNotes/{{Freemasons}}, a loose fraternal association of secret societies which conduct their own private rituals. One difference is that the Freemasons aren't required to keep the simple fact of their membership secret, and many members display Masonic emblems on their jewelry, houses, cars, etc. However, they do tend to be more low-key about it than some of their auxiliary bodies. One of these is the "Shriners", whose members can frequently be seen wearing fezzes with the name of their "temple" (local organization) emblazoned on it in sequins and driving miniature cars around in parades. The Freemasons say that they aren't hiding anything profound, but maintain their secrecy simply because [[IGaveMyWord they promised to do so]]. Whether that's actually the case, only Freemasons themselves know. While in the past they kept a very valuable secret (the techniques of stone masonry; the predecessors of the Freemasons were European trade guilds of stonemasons), whether they also kept ''religious'' secrets from non-members and new initiates remains, well, a mystery.
[[/folder]]
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