Primordials in Exalted are the original gods of creation, birthed from chaos and responsible for just about everything that came after them. They are inscrutable to the point of being Lovecraftian, and tend to focus on one concept to the exclusion of all else. To simplify it primordials are the ultimate munchkins. They're beings so hyper specialized that not only can they not perform tasks outside of their purview, they can't even understand them on a conceptual level.
The Primordials existed since forever in the Wyld, though they were asleep until Cytherea woke up and helped the rest of them do the same (except Oramus, who retroactively became awake for the whole time).
The Primordials are impossibly vast alien beings with multiple souls. Imagine if Cthulhu was the size of Asia and you could meet and hold conversations with his major organs, which had separate identities, and you kinda get the idea.
They each have an overall Soul, which is their being, and that soul is composed of many subsidiary souls. They are defined by their Third Circle souls, and most importantly by their Fetich Soul (though it might be that they define their souls... the Fetich Soul contains their self-identity). Their Third Circle souls have multiple Second Circle souls, which are less important (their deaths affect the Third Circle soul less than the death of a Third Circle soul affects the Primordial). Both the Third and Second Circle souls are independent entities that can be off doing their own thing at any given time. Their Second Circle souls can have independent children (or slaves, or tools, or toys, or excretions, no two species are alike) that are First Circle souls, whose deaths do nothing to the higher souls besides occasionally offend them.
Each of these souls has one or more bodies known as jouten, and the overall Primordial has a worldform jouten (with its own name) that is usually a planet or realm made of their concept (though some settle for impossibly huge creature). Primordial souls are called devas, Yozi souls are called demons (which is more of a political distinction), and undead higher-circle souls are hecatoncheires.
List of Primordials
Although they were originally all bros the primordial war split them into two groups. The collaborators (who got cake) and the loyalists (who got soul lobotomies). And some were killed to death.
An altered Fetich changes the Primordial, a dead Fetich caused the Primordial to implode and become something completely new (but thematically similar), and all Third Circle souls dead "kills" the Primordial, turning it into a Neverborn.
Originally all the primordials were alive, but following the great war only two remain fully intact.
Gaia: Mother of Creation. Being one of the few primordials with anything passing for empathy she wisely sat out the war and survived. Wandered off the edge of nowhere looking for answers and hasn't come back since.
Autochthon: The great maker. Got sick of his jerkass brothers and sisters wrecking his crap and sided with the humans (after operating on his fetich soul to install learning). Like the flatmate of a sociopath he got a little worried about sharing Creation with the now triumphant (and cursed) exalted and decided to sleep outside. Currently has a terminal illness that runs around his body trying to murder the people living inside him, who already had enough to deal with from the fact that his genius never led him to invent the safety rail since machines can't hurt him. Thanks to a bit of DIY brain surgery, he's replaced his fetich soul with himself (if your brain is starting to hurt at this point, that's normal), effectively meaning he's the only primordial able to understand things outside his paradigm; he's still terrible at it, it's just that he's now capable of it to a minute degree, which is more than can be said of the other Primordials.
Malfeas, the Demon City: The Manic-Depressive former king of the Primordials. Even when he was intact he had problems wrapping his head around the concepts that other beings had opinions, or that he should care. Currently sewed inside his own stomach imprisoning his kin (or, if you're feeling unkind, turned inside-out and shoved up his own ass), he wants nothing more than to flip the proverbial table on Creation and start over, though only after torturing everything in it to death forever, at least twice. Hates everything and everyone in Creation... but hates himself most of all. His own Feitch soul despises him and looks down on him, as an expression of Malfeas' own self loathing.
Cecelyne, the Endless Desert: One-time head judge of the primordials and current insane desert, Cecelyne surrounds the Realm of Malfeas in an endless expanse. Her laws aren't as popular these days and mostly consist of "if you can kill it, then it belongs to you," as part of a big, nihilistic thingummy to show the meaninglessness of all law. Word of God says that she is Borderline Personality Disorder incarnate.
She Who Lives In Her Name, the Principle of Hierarchy: - Obsessive-Compulsive She Who Lives was in charge of order and hierarchy back in the day, and recent events have only reinforced her longstanding belief that freedom is the problem with creation. She was only narrowly convinced to give her exalts free will, and seeks to rectify the condition whenever and wherever she can. Also, blew up most of creation in a fit of pique after the war by smashing three of the orbiting crystal spheres that comprise her being into it, irrevocably reducing and damaging herself in the process. May or may not have been Malfeas's lover before both of them went balls-out crazy, and usually has her absurdly-long, problematic-for-the-books'-word-count name rendered as SWLiHN, or Swillin'.
Adorjan, the Silent Wind: Once Adrian, the river encompassing creation, she had her Fetich soul Lilike killed in the primordial war and turned into a howling windstorm. She's not really mad about it though. In fact she's happy as can be. She loves creation, she loves exalts, and she'd love nothing more than to summon up her winds and give you a big hug. Her exalts get a charm to instantly fall in love with people and then get bonuses for hurting them. She hates most sound though, hence the "Silent Wind" (and one of her charms is called Hateful Wretched Noise), so demons of Hell play loud music constantly in order to ward her off.
The Ebon Dragon, the Shadow of All Things: The original sociopath. The elemental embodiment of dickishness, or more simply, opposing other beings from their goals, which is about all he knows how to do (he had this urge before other beings had goals). He is the least mutilated of the Yozis due to a timely surrender and is still capable of (mostly) rational thought. As such he is one of the prime movers in the demon city. He was responsible for cursing the Solars (well telling the others how to do it and fueling it with their dying breaths) and was the driving force behind the Green Sun Princes. He is basically backstabbing everybody all the time, and if Return of the Scarlet Empress is to be believed he is so irredeemably treacherous even his own component souls are scheming against one another. Oh and he's also a stalker. He is such a backstabbing scumbag he occassionally backstabs HIMSELF by not backstabbing people.
Kimbery, the Sea That Marched Against the Flame: The suffocating control freak to Adorjan's deranged stalker. If you're on her bad side she'll consume you under her acidic waves. If you're on her good side she'll lavish you with affection (usually in the form of acidic waves). Nobody survives Kimbery's attentions for too long one way or another. Her demon-blooded descendants in Creation have basically become the inbred yokel pirate mafia.
Cytherea, the Mother of Creation: The Divine Ignition, she is the Big Bang itself. She helped wake the primordials and build creation. Beyond that not much is known about her.
Oramus, the Dragon Beyond the World: When the Celestial Incarnae and the Exalted Host imprisoned the Yozi, they assured themselves that escape was impossible. Then they glanced at the primordial whose entire schtick is "impossible", and realized that extra steps needed to be taken. They broke Oramus's wings, all seven hundred and seventy-seven of them, and wrapped him up inside a shell of his own self. So now the universe's most powerful reality hacker is trapped inside himself, becoming more and more insane. Needless to say, shit is going to get fun if he ever escapes.
Isidoros, the Black Boar that Twists the Skies: A yozi who takes the form of an unstoppable rampaging black hole in the shape of a boar. Likes screwing destiny and penetrating things, dislikes rules and inevitability. Unsurprisingly the cause of mountains of slash fic both in and outside of canon. Currently in a bromance with Szoreny that may or may not include a "b". Most bro-tier of the Yozis, because his purview means that he thinks the Exalted are pretty baller.
Sacheverel, Who Knows the Shape of Things to Come: The Abhorrent Prophet Unimagined. Another yozi who had his fetich soul killed (because that's always a good idea) and turned into a deranged seer as a result. While he sleeps he sees infallible visions of the present. If he should ever wake up he will see infallible visions of the future, forcing everyone to follow what he sees. Nobody wants Sacheverel to wake up. (Except maybe the SWLiHN.) Sachaverel himself is super depressed because he realized he's a character in an RPG and refuses to get out of bed.
Hegra, the Typhoon of Nightmares: A storm of emotions and patron of traders. While she despises phyisical form, she loves fucking with people, demons and humans alike, by inciting riots of random emotions just to see what happens.
Elloge, the Sphere of Speech: Another victim of Fetich death, Elloge got gender swapped and turned into a silently moving sphere of linguistic concepts. Unlike most Fetich deaths, not overwhelmingly terrible for everyone as a result. If you stumble into her by mistake prepare to engage in narrative kung fu battles with the past participle tense.
Szoreny, the Silver Forest: A giant silver forest and mimic. Szoreny loves you, Szoreny hates you. He's the quickest way to travel around Malfeas if you don't mind running through a twisted house of mirror inhabited by clones. Probably the least maniacal of the Yozis, he's working on getting a pardon for himself and his sometimes boyfriend Isidoros so he can
have his revenge at long last live in harmony with creation. (Which may or may not involve conquering it first, but go back and read Malfeas's entry if you don't think that still qualifies him as "least maniacal.")
Qaf, the Heaven-Violating Spear: A mountain with no base or apex, ascending him involves spiritual growth. As his lessons are infinite, his peak can never be reached. Isidoros tried once, starting a classic paradox of incompatible infinities, but reality hasn't actually broken that much: when he got bored and left, his hoovestamp continued the ascent.
Metagaos, the All Hunger Blossom: OMNOMNOM. A gigantic swamp that eats everything that steps within his confines, including abstract concepts, because haven't you been paying attention? Escape his grasp, you'll be riddled with diseases since he's devoured your health. Fail to, and you'll become a part of him as he devour your individuality. You'll know you're getting close when things start turning gray, because he's eaten all the color. There's only one way out of him, in fact there is only one possible direction to go, because he's devoured all the other directions. Not the paths, the concepts of those other directions. He's chewed holes in himself and pieces of his brother primordials have begun to bleed through. Those who pass through may have spent hours and found day have passed, or seconds and come out years later, as Metagaos has been chewing time itself. Adorjan would like him, as he devours sounds, but she likes silence for its solace and serenity, and Metagaos has eaten those things too. Don't ever try to engage in actual combat with him, because he'll probably just win by eating the abstract concept of his defeat and/or your victory.
Mardukth, Who Holds In Thrall: The Mountain and the Beast Upon It. The original king of the Primordials who served as the cornerstone of Zen-mu, the Primordial's original homeland. He could never wrap his head around if he was real or not and spent the entirety of his time in a perpetual existential crisis while asking the other Primordials who he was every other minute. The Ebon Dragon (then the The Dragon's Shadow) introduced him to Malfeas (then Theion, The Empyreal Chaos) who kicked his ass by virtue of being the concept of being the king.
Some of the Primordials were slain before they could surrender, struck down by Ghost-Eating Technique and other such spirit-destroying powers. Since primordials can't even conceive of death, let alone think to program the reality they built to handle it, reality promptly shat a brick and jammed. Now they sit trapped between existence and nothingness, whispering to people about how they should really consider the merits of killing everything everywhere forever. Also, their name is also another name for their still-living kin (there is nothing extra, they just took a synonym and ran with it).
On the one hand, they've effectively been trapped at the very moment of death and can feel the mold eating their bodies forever - killing everything is the best way they can think of to simultaneously do that (freeing themselves from their torment via oblivion) and give one last middle finger to the people that killed them. On the other hand, they could probably just let go of their primordial forms and go off into the wyld again, but they're forever stuck in a self-pitying downward spiral, too obsessed with their own depression and misery to actually improve their situations short of dragging everyone else down with them.
Abhorrence of Life Patron of the Dowager
Father of Murder
He Who Holds In Thrall (while none of the Neverborn are really unique characters, this one was probably Mardukth), patron of The First and Forsaken Lion and the Princess Magnificent
Perfected Principle of Consumption patron of the Bodhisattva Anointed by Dark Waters
Tears of Want
Whose Whispers Chain - worshiped by the Pelagials, a species of manatee-people living in ruined underwater cities in the oceans of the West. Speaks through the mummified corpses of their princes.
The Dragon That Was - What the fuck did you do?! If this guy shows up in your campaign it means you killed the Ebon Dragon (somehow?). There's not much fluff on what this means, except that it's all-but guaranteed to be bad (except when it isn't, like plugging the Oblivion itself).
The Engine of Extinction - Similarly this is the result of what happens if you killed Autochthon, or let him die or whatever. Congratulations on turning one of the few benevolent cosmic entities in the game into the Rape-o-matic 9000.