Outsiders from mythology

Here's a list with a few more that seem interesting. This is only a start. My favorite are the nymphs of stars, they could be like the brijidine azata, without the earth element.

Norse/Germanic mythology

Audhumbla - the primal cow.
Eikþyrnir - stag which stands upon Valhalla.
Gullinbursti - the mechanical golden boar of Frey.
Hamingja - incarnate of luck.
Hrimfaxi - the horse of night, creator of frost and dew.
Skinfaxi - the horse of day.
Tomte - small spirit with immense strength, shapeshifter, cyclopean eye.

Celtic/British

Bean nighe - fairy, an omen of death and a messenger from the Otherworld.
Caorthannach - demon fire-spitter.
Fear gorta - phantom of hunger.
Finfolk - sorcerous shapeshifters of the sea.
Morgen - Welsh and Breton water spririts that drown men.

Greek

Acephali - headless people with faces in their chests.
Akhlys - pale green hag, demon of misery and death-mists.
Almathea - the goat who raised Zeus.
Anemoi Thuellai - wind daemons.
Argus - the hundred-eyed giant.
Arion - a horse with a human voice and two human legs.
Capricorn - Part goat, part fish.
Echidna - Mother of monsters.
Empusae - Servants of Hecate.
Golden-fleeced ram. Better known for its fleece, but when alive it could fly.
Graeae - grey hags.
Horae - personifications of seasons and time.
Kabiri - They had pincers instead of hands, which they used as tongs in metalworking.
Keledones - Golden automaton singing maidens crafted by Hephaestus.
Ladon - dragon, guards the golden apples.
Melione - spectral demon with a retinue of ghosts.
Pleiades - Nymphs of the stars.
Python - earth-dragon of Delphi.
Scolopendra - a many-armed sea monster.
Telchines - magician-smiths and sea daimones.

Roman

Culsu - Etruscan underworld demon who was associated with gateways.
Fulgora - female personification of lightning.
Limentinus - spirit whose responsibility was to protect the threshold of the house.
Mens - persnification of mind.

Slavic

Bauk - animal or goblinoid boogeymen.
Bies - incarnate of anger or a demon.
Gamayun - prophetic bird, symbol of wisdom and knowledge.
Indrik - fabulous beast, lives on the Holy Mountain.
Mora - nightmare spirit woman.
Navi - demons formed out of stillborn children souls.
Paklenjak - a type of devil, ember face, fiery hair.
Psotnik - mischief maker spirit, eladrin?
Shishiga - wood-goblin.
Sudice - Fates.
Vedmak - shapeshifting witcher.

Baltic

Aitvaras - Household spirit, rooster with a fiery tail, turns into a dragon outdoors. Devils sell them for one soul.

Finnish

Etiäinen - messenger spirit.
Haltija - fey.
Riisi - The monstrous offspring of Wind and the ugly Dwarf Loviatar.
Virvatuli - will'o'wisps.

Medieval

Barometz - the Vegetable Lamb.
Ercinee - Phosphorescent birds. Pathfinder 5.
Leontophontes - plant-animals, poisonous to lions. Mentioned in Dragon #199.

European

Aurora Borealis - Angels cast from Heaven who dance forever with rainbow scarves.
Crane Men - human bodies, heads of cranes
Fairy Godmothers - They bring gifts or curses at births.
Krampus - a wicked spirit that gives coal to bad children on Christmas.
Poreskoro - Son of a fairy queen and a demon, this creature has four cat heads, four dog heads, and a snake for a tail. It spreads plague in Gypsy caravans.
Santa Claus - Gives gifts to children on Christmas.

Hebrew

Eisheth - angels of sacred prostitution.
Ibbur - opposite of dybbuk, the most positive form of possession
Ishim - rank of angels is the closest level to human beings.
Lailah - angel of night.
Malakh - messenger angel.
Ophanim - celestial wheels.
Rephaim - race of netherworld giants.
Shamir - mythical worm that disintegrates stone, gift of Asmodeus.
Ziz - a giant bird.

Egyptian

Aau - jackal-headed mummy; guards the entrance to Duat.
Bennu - phoenix.
Nehebkau - man that ate scales of Apep and became hybrid with snake scales and scorpion tail.
Petsuchos - minions of Sobek.

Mesopotamian

Imhullu - terrible wind, elemental?
Kusarikku - demon.
Kullulu - spawn of Tiamat and Apsu.

Persian

Al - demons of childbirth.
Chamrosh - mythical bird.
Khara - cosmic all-seeing creature that watches out for evil in all directions

Arabic

Darda'il - a type of angel.
Falak - serpent that lives under the plane of Fire.
Kiraman Katibin - angelic scribes.
Kujata - a bull with a thousand legs and countless sensory organs who carries the world on his back.
Qarin - a type of genie.

Indian

Apsaras - a type of eladrin.
Dakinis - guardians of the deeper mysteries of the self.
Danavas - type of asuras, cast out by Indra or Rudra.
Devatas - lesser devas.
Gandharvas - guardinal. Demon in Encyclopedia of Demons & Devils 1
Gopis - silver-eyed cow-tending maidens.
Graha - markers of karmic influence.
Kimpurushas - lion-men, leonals?
Kinnaras - celestial musicians, half-human/half-horse or bird
Makara - part elephant, part crocodile. The steed of Varuna.
Pani - dwarf, drought demons.
Pisachas - flesh-eating demons.
Ribhus - celestial artificers.
Vidyadharas - air spirits, like vaati.

Chinese

Baihu/Byakko - the argent Tiger of the West
Celestial Toad - once a mortal woman, she lives on the moon.
Cock of Dawn - the golden rooster at the edge of the world.
Genbu/Gui Xian - the black Dragon Turtle of the North
Hare of Jade - the rabbit that lives on the moon.
Inkpot Monkey - a tiny monkey that drinks ink.
Ryu-O, the green Dragon of the East.
Suzaku/Ho-o - the crimson Phoenix of the South.

Japanese

Earthquake Beetle - A ten-legged giant beetle with the face of a dragon. Causes earthquakes. A.k.a. Jishin Mushi in MC 6 Kara-Tur.

African

Gonafo - a giant African bird, king of all the magical creatures of Dahomey.

Mesoamerican

Aluxob - fey.

South American

Wekufe - like huecuva, evil spirits summoned by kalkus, Mapuche sorcerers.

Native American

Big Heads - giant hairy heads that shoot lightning from their eyes in Iroquois mythology.
Flute Player - an American Indian hunchback. All seeds grow from his hump.
Jackalope - a jackrabbit with antelope horns or deer antlers and sometimes a pheasant's tail.
Kachinas - Rain-giving spirits in Hopi mythology.
Oshadagea - the Great Dew Eagle of the Iroquois. An eagle with a lake on its back.
Si-Si-ootl - A two-headed sea snake with a small human face in the center. Stormwrack.
Skin-walker

American

Babe the Blue Ox

I looked around and these seem interesting:

Greek

Kallikantzaros - malevolent goblins that stay underground sawing the World tree.
Kerkopes - sons of Theia and Oceanus, monkey-like thieves.
Makhai - daemons of battle and combat.
Lampades - nymphs of Hades, serve Hecate. Light of their torches can cause madness.
Mormolykeia - female underworld daemons, attendants of the goddess Hecate.
Pyrausta - it resembles a four-legged insect with filmy wings and a dragon's head. It lived in the fire like a salamander and died if it went away from the fire.

Norse/Germanic

Drude - possessed virgins or priestesses. Take the form of hags associated with dreams. Able to creep into homes at night through the smallest of openings, and can appear as feathers, clouds of smoke, bumblebees, snakes or toads.
Erlking - deadly fey.

Celtic

Buggane - ogre and mole-like, sent by the fey to punish.
Bugul Noz - incredibly ugly but kind Breton fey, last of his kind.
Fear Liath More/Grey Man - has a powerful psychic effect of overwhelming negative energy leading to panic or suicidal thoughts. Fits in Annwn.

Slavic

Rarog - a hawk, falcon, or fiery dwarf who turns himself into a whirlwind.
Rübezahl - a trickster giant, gnome or mountain spirit, lord of weather.

Other European

Caballucos - when the people make bonfires to purify their souls, giant dragonflies appear amongst the ashes, these are the souls of sinners, and they come to release their fury over a year's worth of sins with fire and terrifying screams.
Kaw kaw - slimy greyish bogey man who strolls the streets at night. He is able to smell a person's guilt and is capable of entering their homes by extending and contracting his snail-like body through any crack or fissure.
Ördög - Hungarian demon, looks like a black faun, dwells in the underworld constantly stirring a huge cauldron filled with souls. It is his habit to make bets with humans to see if they become corrupted.
Tartaruchi - keepers of Tartarus. Described as using one hand to choke damned souls, and the other using an "iron of three hooks".
Trenti - Cantabrian imp, this annoying but not malicious goblin is very difficult to see because it lives deep in the forest and resembles mushrooms, leaves, and moss.
The Wooden Mother - Bosch's hag, her flesh is twisted into petrified wood and her lower body mutated into a corpse-pale serpent's tail, she coddles a mummified infant and rides a great bloated rodent through the desert.

Persian

Agas - fiend of plagues and diseases, has the evil eye, it was believed that Agas tempted others to commit sins that are perceived or performed by the eye.
Shadhahvar — antelope with a single hollow, branching horn. The wind blows the horn like a flute, and animals are drawn toward the pleasant music. Then, the Shadhahvar kills them.

Indian

Tripurasura - Hindu fiends.

Turkic

Abaasy - Yakut fiends, they eat souls and give diseases, madness, can be appeased by blood sacrifices.

Chinese

Fei Lian - a celestial monster with the body and legs of a stag, the spots of a leopard, and the tail of a serpent. Its sparrow-like head has bull horns. It controls the fierce storm winds, releasing them from a bag at whim.
Hundred-Heads - gigantic fish with many heads, each one that of a different animal. Legend holds that the fish was the reincarnated spirit of a monk who had often called others "monkey-head". The karma of these insults had made him return as a monster.
Hundun - legendary faceless being of chaos, primordial or protean.
Qiong Qi - beastly fiend that can swallow evil spirits, punishes the virtue and awards the evil.

Japanese

Amanojaku - demon, it is thought to be able to provoke a person's darkest desires and thus instigate him into perpetrating wicked deeds. Kidnaps or devours people, and sometimes impersonates by wearing their flayed skin.
Amazake-babaa - hag, she comes to the doors of houses at late night asking for amazake in a child like voice, but if anyone answers they fall ill (pox).
Binbōgami - a kami who inhabits a human being or his house to bring misery and poverty, appears as a skinny, dirty old man, with an uchiwa in his hand.
Enenra - yokai of smoke, can only be seen by the pure of heart.
Harionago - beautiful woman with extremely long hair tipped with thorn-like barbs, and she uses it to ensnare men.
Hyakume - yokai guardian of shrines, one of his eyes would leave his body and endlessly pursue the thief until it made contact. Thereafter the thief always had the eye as a mark that he was a thief.
Inugami - dog-like kami, masters of black magic, are evoked for criminal activities.
Kamaitachi - yokai, three fast weasels with sharp claws, riding on a gust of wind and cutting people.
Namazu - giant catfish who causes earthquakes. Aboleth?
Nekomata - yokai of cats, necromantic powers.
Ushi-oni - monster with a horned, bovine head, and a sword for a tail, it is thought to drive away evil spirits.

Mesoamerican

Xolotl - as skeletal dog-headed psychopomps.

South American

Cherufe - magma monster, could serve Chlimbia.
Chullachaqui - shapeshifter, jungle spirit, hunts those who break taboos.
Invunche - a giant, hairy blood sack with twisted limbs, when it hungers, it sends out its octopus-like minion to tentacle-lasso a few young girls from the lakeshore. Then this bloated monstrosity drains every drop of their precious blood. It is also served by packs of furry, gray cannibals known as Chivatos. These wretched creatures feed on the drained remnants of the Invunche's blood feasts and were once children themselves, transformed into beasts by the evil warlock who oversees the entire grotesque menagerie. The warlock sews up the poor child's orifices and then feeds it a strict diet of goat and child flesh. In time, the toddler metamorphoses into its final form. With the right torturous, loving care, a Chivato can even become an Invunche.
Ole Higue - Guyanan vampire capable of discarding her skin, at night she transforms herself into a ball of fire.

Native American

Achiyalabopa - Pueblo celestial bird, described as being of extraordinary size and having rainbow-colored feathers as sharp as knives.
Black Tamanous - a cannibal spirit that presided over the destruction of the Earth to rid it of the great primordial beings.
Chapa - Lakota beaver spirit and lord of domesticity, labor and preparation. Guardinal?
Mishipzhiw - it has the body of a cat with a spiked back. It captures its victims with its long tail, and creates storms by waving it in the water.
Nalusa Falaya - Choctaw shadow beings, if people allow evil thoughts or depression to enter their minds, it would creep inside them and eat their soul.
Spearfinger - appears a harmless old lady, has stoneskin and an obsidian finger used to cut her victims. Her mouth is stained with blood from the livers she ate, she clutches her right hand tightly, because her hidden heart and only weak spot is in her right palm.
Tsi-noo - A person from Abenaki myth whose heart is made of ice and has no soul; he eats the souls of others for sustenance and strength.
Wakandagi Pezi - a water serpent that has deer like antlers on its head and hooves on its feet. Shoots out water bombs.

Inuit

Ijiraat - elusive shapeshifting (except for the red eyes) spirits, surrounded by mirages, cause memory loss.
Inupasugjuk - artic giants, catch humans to use as playthings.
Mahaha - maniacal arctic demon. This creature is described as a thin sinewy being, ice blue in colour and cold to the touch. It takes pleasure in tickling its victims to death with sharp vicious nails attached to its long bony fingers.
Taqriaqsuit - shadow people.

African

Adze - Ewe witches, takes the form of a vampiric firefly, can possess people.
Aziza - beneficent Dahomey fey, known to have given practical and spiritual knowledge similar to that of Prometheus. Are said to live in anthills and silk-cotton trees. Aziza was a god who has not suffered oblivion like the others from lack of worship, just shrunk into insignificance.
Obayifo - Ashanti vampire skinchanger witch, able to travel as a ball of light and possess people. Believed to kill children by remotely sucking their blood and and to suck the life from the land and weaken crops.
Shetani - East African evil spirits, various weird forms.

Aboriginal

Yara-ma-yha-who - a little red man who drains the blood of its victims using the suckers on its hands and feet, then consumes and regurgitates them several times until they are transformed into a yara-ma-yha-who.