We're going to have an interesting and different ladies-of-myth blog today thanks to this request: I was wondering if you could tell us more about the Greek Trickster goddess Eris, and all her shenanigans. Eris is surprisingly popular and well-known in modern pop culture, considering that she wasn't particularly beloved during ancient Greek religion, so she's a neat topic to explore.
First of all, I have to disagree with you (good-naturedly, though), friend - Eris is definitely not a trickster goddess! In mythological terms, a trickster is someone who rebels against established rules, order or authority, usually through cleverness, and most often as a means toward creating, liberating or enabling something creative and new. Tricksters tend to cause problems and upheaval through their misbehavior, but that upheaval often has positive consequences, such as the creation or distribution of new things or the realization of flaws in the current order that can be corrected.
You could argue that the episode with the apple that leads to the Trojan War is kind of a trickstery move on Eris' part, but for the most part, she doesn't do all that stuff. She tends to operate within the rules of the universe, not outside them, and there's pretty much nothing positive that ever comes out of anything she does.
Eris is the ancient goddess of discord and strife - and not the fun kind of discord where things are just sort of disorganized and quirky and excitingly non-conforming, but the horrible awful kind where everyone violently hates one another and everything gets destroyed. The ancient Greeks were terrified of Eris, who represented the horrors of warfare, violence, hatred and cruelty, which she visited on humanity whenever she had the chance on her own, and which she could also come down to inflict on the orders of Zeus or Hera, who set her loose to punish miscreants that they believed deserved it. We talk a lot about how awesome mythological ladies are around here, and Eris is certainly awesome, but it's the original meaning of the word awesome here - inspiring fear and awe, and the feeling that maybe you're in over your head.
In case you were wondering how much the ancient Greeks did not like this goddess, the laundry list of her most common descriptions refer to her as "hard-hearted", "harsh", "cruel", "abhorred", "unwholesome", "relentless", "wrathful", "wearisome", "death-bringing" and about ten thousand other words meaning that she's terrible and everyone wishes she were not around. In fact, although her name is most often translated into English as "strife" or "discord" (especially since the name of her Roman equivalent, Discordia, grew into the latter word in English), other translations make the name closer to "hatred". She is literally hatred for other people personified.
Eris' scariness is established partially by her familial relations, which are a giant roster of ancient primordial powers and figures that represent horribleness and awfulness in varying ways. Hesiod lists her mother as Nyx, the primordial night, a goddess so terrifying that even Zeus in moments of greatest wrath refuses to cross her; Hyginus expands this to also list her father as Erebos, personification of darkness itself as well as a living part of the underworld. Her siblings include such un-favorites of humanity as Apate (goddess of deceit), Geras (god of old age), Ker (god of violent death), Momos (god of mockery), Moros (god of doom), Oizys (goddess of misery), Nemesis (goddess of punishment), the twins Hypnos and Thanatos (gods of unconsciousness and death), and of course the Keres, the blood-drinking dark sister-triad to the Moirai or Fates, who inflict doom upon soldiers in combat and drag dying men off the battlefield and into Hades to feast on. There are a few nice siblings in there, like Philotes and Misericordia, but they can't really prevent the entire family from being a sort of primordial soup of terror and human suffering.
As if her immediate forbears and siblings weren't scary enough, Eris also has children of her own, and among her brood there are no nice people whatsoever. Her list of children includes Dysnomia (goddess of anarchy), Horkos (god of punishing oathbreakers), Lethe (goddess of forgetfulness), Limos (god of famine), and Ponos (god of toil and work); and she is also responsible for bringing into the world several sets of multiple siblings bent on a single distressing task, including the Algea (in charge of causing pain), Amphilogiai (in charge of legal disputes), Androktasiai (in charge of manslaughter), Hysminai (in charge of brawling), Makhai (in charge of battles), Neikia (in charge of arguments), Phonoi (in charge of murder), and Pseudologoi (in charge of lying). My personal favorite of her brood is Ate, who is literally the goddess of bad ideas, and whose interference is responsible for almost every time a hero in Greek myth makes a dumbass decision that gets them killed.
Hesiod actually hated her collection of children (together referred to as the Lugra, meaning "banes") so much that he decided to poetically declare that they were the daimones of all bad things in the world that were originally sealed in Pandora's jar, thus literally making Eris and her children the worst things to ever happen to the universe.
At any rate, Eris' most famous tale is of course that of the beginning of the Trojan War, although in reality she isn't actually involved all that heavily. When Thetis and Peleus (later to be the parents of Achilles) are being wedded, which is a big deal to the gods because of the prophecy that Thetis' child will outshine his father and everyone's need to make sure they safely know who that father is so no one accidentally sires a super-baby, Zeus invites every deity in the pantheon except for Eris; no one gives an exact reason for this, but presumably they didn't want her there because, well, she's terrible and causes all of the problems in the world.
In ancient Greek hospitality terms, however, this was a massive slight to Eris' reputation and honor, and when she arrived and was refused entrance to the banquet, she instead hurled a golden apple through the doors into the middle of the feast. The apple was inscribed "to the fairest", and the ensuing fight between Aphrodite, Hera and Athena over who it was supposed to go to led to Paris acting as judge to choose one of them, which in turn led to Aphrodite rewarding him for choosing her by giving him Helen as a wife, which in turn touched off the entire gigantic Trojan War debacle.
Whether Eris knew she was causing the Trojan War or not is debatable, but she certainly knew that she was causing a political meltdown, which it's pretty obvious was exactly what she wanted in order to get revenge for being left out of things. Alas, as is usual in Greek myths, trying to avoid inevitable things like a fight breaking out at a wedding just makes it more certain that they end up happening, usually with gusto.
Whether she caused the war knowingly or not, she was certainly perfectly happy to participate in it. Because war, especially violent and bloody war that lasted too long or did not conform to the rules of battle at the time, was considered one of the ultimate expressions of chaos and disorder, Eris was considered one of the foremost deities who gloried in it and tried to cause slaughter whenever possible. At the Trojan War itself, Homer describes Eris striding into battle with Ares, beginning as only a small woman but growing until her head strikes the heavens and raining down bitterness and hatred upon all warriors on both sides of the battle. She also appears to the Greek fleet, on Zeus' orders, to give such a mighty and terrible battle cry that they are motivated to go on fighting tirelessly, and once all the other gods have withdrawn from the war on Zeus' orders, she alone remains, spectating with pleasure as the warriors kill one another "like wolves".
Eris' connection to Ares here is not a coincidence; while the ancient Greeks appreciated martial might and warrior prowess, they also viewed bloodlust and chaos on the battlefield as highly distasteful and dangerous to society, which is why Ares himself was well-honored by soldiers but not someone anybody was inviting to their polite society parties. Like Ares, Eris represents loss of self-control and the dissolving of ideals ilke honor and glory into the horrors and mutilations of war, and when the inevitably ugly side of combat appears, there she always is. Homer actually calls Eris the daughter of Ares; he may be conflating her with Enyo, a daughter of Ares who is a war goddess also associated with terror on the battlefield, and simply drawing a parallel between the two, although there is still scholarly debate over whether or not Enyo is supposed to be the same person as Eris and how the genealogy is supposed to work if that's true.
And of course, since if there are wars out warring Eris is most likely to be found causing problems in them, she is also present during the Indian War, when she appears to Dionysos in a dream and reproaches him for not getting into battle faster, saying that the other gods are making fun of him, she's ashamed of him, and his endless frolicking about having a good time makes him a lazy good-for-nothing who doesn't deserve to be classed among the sons of Zeus. Dionysos promptly wakes up and starts waging some kickass wars on basically everybody, because when someone calls an ancient Greek dude a wuss who doesn't deserve his family name, that's generally their first response. Ironically (or not, for her), she then also turns up fighting in the war on the side opposite Dionysos, sowing havoc among his troops as she accompanies Ares again.
Interestingly enough, Hesiod claims that there were originally two goddesses named Eris. He says that one is the good Eris, in charge of healthy and beneficial forms of strife like competition that encourages both sides to become better and motivation to encourage people to achieve what they are jealous of in others, but the other is the bad Eris, who causes marital strife, social chaos and physical violence. He is alone in this particular vision of a double version of Eris, but there is some scholarly suggestion out there (when is there not?) that suggests that since Hesiod seems to view Pandora as a sort of double of heavenly Aphrodite, he may be therefore creating a positive version of Eris to serve as the hope left in Pandora's jar as the same sort of literary device.
For those keeping up with the modern religious scene, you may have heard of Discordianism, which is a mdoern-day religious movement begun in the 1960s which claims Eris as its major deity. Discordianism is basically concerned with the idea that most of life is an illusion, and that since all of our perceptions of it are just signals sent to our brains to make sense of, there is no such thing as objective reality and the truth of the universe may actually be vastly different from the way we are able to perceive it. Because the only universal constant in this idea is that chaos exists and is the major moving force in the universe, Eris was chosen to become the philosophy's main figurehead. The Discordian version of Eris is significantly less scary and dangerous than her ancient Greek counterpart (in fact, Discordian religious texts directly make fun of the ancient Greek idea of her as being so terrible), and tends to use her more as a symbolic idea to represent chaos rather than an actual deity for ritual and worship (although of course her importance varies depending on the particular Discordian in question).
There is all kind of argument over whether or not Discordianism is a real religion, thanks to its obvious elements of parodying other religions and the tongue-in-cheek attitude of many of its adherents when questioned about it or asked to explain what it means, but its existence means that Eris' name has surprisingly survived and remained semi-relevant in pop culture long after most other minor Greek deities' were forgotten. It's ironic that she would remain actively worshiped, even in parody, when many other more popular gods' worship is all but forgotten, but that's the kind of cruel irony Eris is known for, after all.
You will note that there is not a ton of art in this post, and there is a good reason for that: the ancient Greeks didn't like Eris very much, so they didn't spend nearly as much time committing her to artwork as they did for deities that they did love and want to honor, and they weren't exactly excited about the idea of having an image of her in their home, business or temple for fear of the inevitable chaos that would follow from her presence. Heroes might want to take a page from their ancient playbook; Eris may be someone that should never be disrespected or ignored, but it's also probably not the best idea in the world to invite her to get involved in your affairs, either.