Guardian Entity

""Man, what I would give for a godlike protector of my own... Something more... feminine, perhaps...""

- Winfield, Record of Agarest War

The Guardian Entity is a being that protects their ward from harm. Usually, they spend most of their time floating invisibly and intangibly, preferring to subtly steer harm away from their ward, and only materializing when necessary. But when they do appear? They will lay a smackdown for their trouble.

Their nature can vary quite a bit. Usually they're benevolent, but of course that may not extend past protecting their ward so they can fulfill a dark fate. They may be the ghost of a loved one, a fey entity that torments and protects in equal measures, a classic Guardian Angel, or a demonic entity there to protect the Anti Christ. Depending on their nature, the entity and ward will have a very interesting relationship, but it's not impossible for a really subtle entity to avoid being noticed at all by their ward.

In terms of strength, it might only be able to nudge butterflies, or fully embody the Sidekick Ex Machina and bring down the Wrath Of God/Satan/Crystal Dragon Jesus on those who look funny at their ward. Speaking of that, the Guardian Entity is often its own master rather than completely subservient to its ward; in such a case, while it may take some input from said ward, it chooses who to hurt and how to do it all on its own. This can be especially nightmarish for the ward if they are psychotically overprotective, and oversensitive or inscrutable as to what they consider "threats" to their ward.

See also and compare Kid With the Leash and The Kid With the Remote Control, where the ward actually controls the entity, which is corporeal and evil. Also related to Sidekick Ex Machina, Puss in Boots, Mon, Guardian Angels, and Fairy Godparents. Threshold Guardians may be this if fully aware of their role as "Obstacle to ensure that character is strong enough to face what's after them."

Anime & Manga

 * The Stands from Jo Jos Bizarre Adventure are the Trope Codifier for most Japanese media. Stands are a manifestation of the user's soul and the user dies if his or her Stand is destroyed, but they are incredibly powerful.
 * Yu-Gi-Oh: Guardian Eatos, as well as the other Guardian cards, were this for Rafael, at least after the storm that killed his family.
 * The kas in the Memory World arc are the same, and the slabs they can be bound in make it clear that the slabs/original cards are essentially portable Guardian Entities. Otherwise, they act almost exactly like JoJo Stands, right down to being Invisible to Normals.
 * Yubel was created/recreated/transformed from human to dragon/fiend/her standard form that we first knew her in in order to guard Juudai, the person with the power of Gentle Darkness, until he became an adult. She kind of overdid it with the protection angle, though.
 * The Pharoah himself. Especially in Season Zero.
 * Neon Genesis Evangelion has its own take on the guardian entity in the Evangelions themselves.  The Evangelions berserk, going stright from Giant Mecha to Nightmare Fuel as they render the target completely silent
 * The Guardian of Tsukasa in .hack//SIGN which is definitivly on the overprotective and very brutal and trigger happy side of things. Tsubasa isn't very happy about this, and the rest of The world even less.
 * Naruto:
 * Shukaku acted as this for Gaara when he was young. The sand protected him from any harm, but also tended to react to people who cause him emotional harm, making his abilities unstable. Later he learned to control it... after crossing the Despair Event Horizon.
 * The Mangekyou Sharingan grants its users the ability to form Susanoo, a chakra-based warrior entity that grants absolute defense and a variety of amazing offensive measures.
 * Naruto himself can rely upon his Tailed Beast to lend him its assistance in times of need.

Comic Books

 * Mister Immortal of the Great Lakes Avengers (X-Men, Champions, Initiative, etc.) had Deathurge (who is exactly what he sounds like) as his "imaginary" childhood friend/guardian.
 * Guardian Angel of PS 238 has an 'invisible friend' who protects her from harm both direct and indirect. If she's attacked, she simply seems to have an active forcefield that repels objects. If she walks out past curfew, the surveillance cameras somehow just fail to record her and anyone else nearby (after all, if they'd get caught, she'd get caught with them). If she walks out in the rain, it never hits her.
 * The Guardian later switches to become more reactive than proactive ; at one point Emerald Gauntlet successfully hits her with a paper airplane, but the Guardian immediately picks it up and sends it back at him.
 * In Midnight Nation, a robed figure carrying a flaming sword protects Laz (the Biblical Lazarus). The guardian is mostly off-panel, and is never seen actually doing anything -- just putting in an intimidating appearance does the job.

Mythology and Religion

 * The concept is really Older Than Feudalism, with Zoroastrianism (scholars disagree about when this religion originated: it goes back at least to 5th century BCE Persia, and maybe to between 18th and 10th century BCE). Each living person is believed to be a part of a greater being, "fravashi", which separates from it upon birth and reunites with it four days after death. During the person's life, however, their fravashi acts as a Guardian Entity for him/her.
 * Hesiod (ca. 700 BCE) claimed in his Works and Days that the extinct humans of the Golden Age became guardian spirits for the future generations. Plato (428–348 BCE) merged Hesiod's idea and the Zoroastrian concept and placed the result into his philosophy as "daemons".
 * The Zoroastrian concept also entered Judaism, presumably, around the time of or after the Babylonian Captivity (597-538 BCE), along with many, many other things, thanks to cultural osmosis. Since then, the Bible has mentioned on several occasions that inviduals and entire peoples have guardian angels assigned by God to watch after them. The idea was later adopted, almost without change into some Christian traditions.
 * Islam has a similar concept, "Kiraman Katibin", though these "guardian angels" don't interfere with the person's life but record all actions he or she performs. There are also the "qarin", jinn-like spirits assigned to each individual as companions.
 * Some Native American nations have a Rite of Passage called "guardian spirit quest" (The Other Wiki calls it "vision quest"). In this ritual, a boy fasts and meditates for several days to receive a visitation by an animal spirit who henceforth becomes his guardian and imbues him with some of its (magical) properties.

Literature

 * In The Twelve Kingdoms, one of the later arcs concerns a Kirin who wound up getting stuck in the human world with amnesia - used to be he was bullied for being 'weird', but unfortunately, he has guardians: The Youkai he took as his servants back in the Twelve Kingdoms, acting from the shadows to keep him safe. Unfortunately, they don't have a lot of restraint, and resultingly, anyone who shows him the least bit of hostility or unkindness winds up having 'accidents', including a few deaths...
 * In Good Omens, Crowley (a demon) and Aziraphale (an angel) act as this to the Antichrist. Or try to, anyway.
 * In The Dresden Files, Harry has his own Fairy Godmother, who, as revealed in Changes, as part of her deal with his late mother.
 * In This Rage Of Echoes, the protagonist has an imaginary friend that looks like a mummy. This doesn't seem to be important other than insight into Mason's personality. That is, until he realizes that the evil copies of himself can see it and are absolutely terrified of it. It still seems like a shared hallucination though,.
 * The titular character from Ella Enchanted has her own fairy godmother who's been in her family for generations.

Video Games

 * Gardevoir from the Pokémon series towards its trainer (and possibly friends/relatives of the trainer).
 * It's right there in the dex entry; which states, "Gardevoir will try to protect its trainer with its life.".
 * Cid from Final Fantasy XII has one of these in the form of Venat.
 * Persona in the Persona series. Regardless of the game, you must have a persona to be able to defend yourself from shadows.
 * Servants from Fate Stay Night have shades of this, being able to go into a sort of spirit form and watch over their Masters.
 * In the first Kingdom Hearts game the Big Bad Ansem, Seeker of Darkness (pictured) summons a shadowy being he simply calls Guardian to fight for him. In his One-Winged Angel form he even fuses with it and a giant battleship.
 * He continues to use it in his reappearances in future Kingdom Hearts games, most notably in Kingdom Hearts 3D,
 * Record of Agarest War's Ellis is protected by Borgnine, a lesser god. However, Ellis isn't exactly weak herself.
 * Ellis's expy Alice in ZERO has this in Galios.
 * This makes Agarest 2's Fiona the only playable full-blooded High Elf in the series not to get her own guardian.
 * The player acts as one in Baten Kaitos. As a Guardian Spirit, the player aids the spiriter Kalas in his travels.
 * Dizzy's wings Necro and Undine are this to her in Guilty Gear. They are especially violent about it, as well.

Webcomics

 * In Blip, Lucifer himself is this for K. He protects her because he's convinced that she has the power to destroy the world.
 * In Homestuck, Guardians are support characters, often family members. The trope, however, applies to the sprites - ghostly entities that can protect and guide the main characters. Guardians do tend to end up as sprites as well, though. Additionally, each planet with a sapient species has a godlike First Guardian. At first one would think that they're there to protect the species as a whole, but no, not really. They're there to protect those who are fated to play the Game of Creation until they start the game, and will inevitably leave the rest of that planet to die when the time comes.
 * In the Ciem Webcomic Series, Angie becomes this for her mother Candi - in a dream, at least.

Web Original

 * SCP Foundation-204, a "semi-organic nano-machine colony" which follows a kid around, and eats anyone who endangers the kid. (Or anyone the kid tells them to eat.)