Gate of Truth
"It was like all the information in the world was being poured into my brain at once. My head felt like it was about to burst, but for an instant, it became clear: the truth of everything."
—Edward Elric, Fullmetal Alchemist
The Gate of Truth is a central nexus of all knowledge in the universe, or something close to that. Tends to be difficult, if not nearly impossible to reach. If the answer is Forty-Two, then chances are, the question is somewhere in there. It may or may not be sentient, and may or may not be actively collecting knowledge, but what's important is that it already has a lot of it in stock. If it's known at all to people, those who know about it are very likely to be an elite of some sort, and will more likely than not be killing each other just to get there.
God, or something like that might be guarding it to protect all the secrets within, if they are not the same being as the gate itself. Else, there's probably a toll-keeper who requests a small fee before you can take a peek at its vast repository. The point is, the knowledge is collected, and a block has been installed that keeps everyone from just wandering up and partaking of it.
Whether or not the knowledge gained was worth the cost depends on which end of the Sliding Scale of Idealism Versus Cynicism the story lies.
Note that the Gate of Truth need not necessarily be a literal gate. It could be a tree, a scary door, or even the corner of Rhodes and Fourth Street. "All knowledge" need not be a literal description, either. Simply a lot will do.
- The Gate of Truth from Fullmetal Alchemist. Truth, a white, featureless, Jerkass Gods godlike being whose physique matches that of the person entering his realm, is the gatekeeper. You pay with a part of yourself, which Truth then wears until you reclaim it, assuming you ever do; in exchange, you gain the ability to perform alchemy without a transmutation circle.
- At the end, it is revealed that it is possible to pay with your Gate instead of your body parts; however, this renders the alchemist unable to perform alchemy ever again, and unless he somehow is tied to another person's gate, will strand him in Truth's realm until he dies.
- Works slightly differently in the 2003 anime version. There is no gatekeeper; rather, the Gate itself is implied to be sentient. Also, the Gate is, in fact, a portal between the world of the series and our own world, and thus the source of the soul energy that powers Alchemy. It is inhabited by weird black imps that do the body part-claiming in Truth's stead -- and for a short period of time, the homunculus Wrath until Ed provides him with a means of escape. It's implied the imps are actually the souls of those who die in our world.
- Mnemosyne has Yggdrasil actively trying to become this by casting time spores on the world and using them to gather data.
- Parodied in Cowboy Bebop when Spike and Jet brave the perils of a flooded, crumbling museum to retrieve the last working Betamax machine so they can read an ancient tape. The contents of the tape and their effect on the crew seem to play this trope straight though.
- No, they took a VHS player, because "Bigger is always better" and Spike wasn't paying attention earlier when the difference between VHS and Betamax was being explained. They get back to the ship with a VHS player, and realize the Betamax doesn't work on it.
- The Galactic Leyline from Outlaw Star is mainly one of these, though it also grants wishes. If you can reach its center in one piece.
- The quantum computer from Gunnm Battle Angel Alita: Last Order. It uses the collected brains (the collective unconscious of humanity) as a means to predict the future. Zalem keeps it a heavily guarded secret from everyone.
- In The Odyssey, there are two gates through which all dreams pass, one of horn and one of ivory. Dreams that pass through the horn gate are true (that is, they come to pass in Real Life), whereas dreams that go through the ivory gate are deceptive and false.
- Speaking of, in Neil Gaiman's Neverwhere, the angel Islington guards, among other things, the door to Heaven, hidden in the deepest part of the London Underground.
- From the Cthulhu Mythos, Yog-Sothoth is the Gate. Yog-Sothoth is the Key. Yog-Sothoth is the All-In-One and the One-In-All. Past and present are one in Yog-Sothoth. He alone knows where the Great Old Ones walked the Earth's fields, and He alone knows where they shall do so again and why none can behold Them when They walk.
- "Deep Thought" from The Hitchhiker's Guide to the Galaxy.
- The vignette "A Man Before the Law" in the Franz Kafka novel The Trial is a subversion, in that the man trying to enter the gate that leads to the law itself never gets to entire despite spending an entire lifetime trying to learn the required price.
- Many fictional uses of the Real Life Library of Alexandria, which was lost or destroyed depending on which story you believe, have it become one of these.
- In The Dresden Files, The Archive or "Ivy" is a living example, as she knows everything that has ever been written, and is updated in realtime, to the point that Harry sends her a note using this. Its a bloodline ability, passed from daughter to mother.
- The Black Library in Warhammer 40,000 contains every piece of information about Chaos ever collected. It exists in an unknown location deep in the Eldar's Webway, is guarded by the secretive, dangerous Harlequin cult of Eldar warriors, and only a handful of humans (most notably the Emperor) have ever reached it. Considering that much of the information is Things Man Was Not Meant to Know, the security is necessary.
- A.B.A's instant kill attack in Guilty Gear causes one of these, inscribed with the Kabbalic Tree of Life to appear, open, and suck the enemy in on a successful hit. The door slams shut, and is then locked shut but her giant monstrous key. "Destroyed!" intones the announcer.
- In the lore for The Elder Scrolls, Hermaeus Mora's plane of Oblivion is an eternal library where all forbidden knowledge can be found.
- The Elder Scrolls themselves are basically a portable version of this, since they contain the secret to the very fabric of the universe... and if you try to just read one normally, you go temporarily blind.
- The Matrix of Wisdom from Transformers Generation 1. When opened, it destroys an intergalactic Hate Plague by unleashing its accumulated wisdom.
- Wan Shi Tong's Spirit Library in Avatar: The Last Airbender is this, complete with scary spirit guardian.
- For that matter, so is the spirit world itself, where Aang has to brave various monstrous terrors so that he can ask questions of his previous incarnations.
- An episode of Justice League features the library of Hades himself, located in you-know-where.