Erinys (Fury Devil)

 The erinys' (not sure if that's the correct plural? feel free to correct me) are the archetypical fallen angel. While perfectly capable of holding their own in a fight, it also has a rather high deception bonus, and some neat illusion spells - meaning she (or he) will try to sway you and lead you astray first, and will only fight you if they're out of options (or you know... if you really, really manage to piss them off)

Sorren Skyspear is an overly zealous and often violent aasimar inquisitor. His entire life, he has been dreaming of meeting his angellic progenitor. When he finally gets the chance, it's in the middle of a battle with some Outer Ones' cultists - and she is majestic in her holy violence. Enthralled with her nigh-divine presence, he hops along with her on missions of divine retribution. When he realizes that the missions have been more and more violent for smaller and smaller slights, and that his "progenitor" is no angel, it is almost too late for his soul.

After a long life spent in one adventure after another, Lord Durnsdale retires to his estate. Deciding to finally live his life as the noble he was born as, he takes for himself a bride, a beautiful young woman named Jolene he met during one of his many adventures. Jolene, herself highly educated, takes an interest in helping the good lord rule over his people. Secretly, she also keeps slipping mind-numbing poisons in his mead, until she finally has practically free reign over their estate. Luckily, the lord has yearly reunion feasts with his old crew - whoever remains alive of them, at least - and some of them are bound to notice something is amiss.

Rapunzel is a crafty Erinys devil living in an enchanted tower in the middle of nowhere. Using illusion spells to disguise ropes as his unnaturally long and majestic beard, he lures would-be saviours of both genders to his abode. Once there, he uses seduction and charms to lull the heroes into feeling safe, at which point he strikes, chaining his victims and dragging them to the hellish dungeons beneath the tower, where he tortures them until death.

Elephant

 The elephant in the bestiary comes in two variants, a regular one and a mammoth, with the mammoth getting an additional two tusk attack to improve action economy and resistance to cold environs, over the elephant's already impressive grabbing trunk and tusk attacks.

It is common knowledge that the great mammoths of Ledenya plains "bury" their dead. What isn't common knowledge is that mammoth graveyard locations aren't randomly chosen - each of them actually lies on a confluence of ley lines. While humanoid graveyards tend to corrupt the ley lines, infusing them with necrotic energies, the lines passing through mammoth graveyards carry with them primal energies, responding to primitive but strong concepts of bond, survival, and family.

The Sourside jungle is deeply magical in nature, every speck of soil and every leaf on a tree containing residual magic. The amount of magic remaining in a corpse beyond its death responds to the amount of life force it held in life - and elephants, being among the largest denizens of the jungle, are often targeted to harvest it. Both the Hunters' Conglomerate, who offer heaps of blood money, and the Druidic circle opposing them, who offer nothing but a clean conscience, are looking for recruits in the struggle for power in the jungle.

A necromancer decided to usurp an elephant graveyard. He conducted a ritual to raise up an army of zombie elephants, but instead, what rose up is something that has never been seen before - a necrodont, an lumbering, skeletal elephantine creature that is made up of dozens of elephant skeletons. The necrodont promptly trampled the necromancer, before proceeding to go on a rampage in the surrounding countryside. Curiously, the creature never attacked a single animal, nor a druid who hadn't attacked it first - while humanoids were killed left and right. Attempting to combat the massive undead being is a last resort option, but sages suggest the graveyard might hold a key to laying it to rest without engaging it directly.

Elemental, Water

 The water elementals in the bestiary include living waterfalls, quatoids, tidal masters, brine sharks, and elemental tsunamis. Most of them are either penalized for not standing in water, or have abilities that benefit from being in open water. While you *can* stick one of them in a pool and have your players surprised and scared, encountering these in the open sea (or, you know, on their home plane of water, that is... all water?) makes for so much more drama.

The Untari jungle is known for its many streams and waterfalls, but any attempt to map their locations is futile, as they appear to be changing places. Indeed, the jungle is a place of thinning, where the material plane meets the plane of water, and the many living waterfalls who keep crossing over find it very fun to move the streams and rivers around. However, they are very shy and secretive about it, and if mortal eyes see them in action, they might grow violent.

The Angulii pass, a stretch of sea between Northlandia and the polar ice caps, is known for its treacherous waters. Many terrible aquatic beasts lurk here, but among the most feared are entire schools of brine sharks. These elementals are said to jump dozens of feet up into the air, dragging sailors with them and plunging them into the cold depths of the ocean. Some of the more experienced sailors claim that offering them fresh water might keep them off - while others dismiss it as dangerous and wasteful superstition.

The Blue Brothers were the twin tidal master guardians of Akhtana Archipelago. One day, a group of small, octopus looking elementals appeared and whispered something into the brothers' ears. The brothers immediately nodded and then left into the deep, never to be seen again.
As the Calamity, an elemental tsunami that visits once every fifteen years, approaches, the islanders must choose: will their strongest and most capable try to stand against the Tsunami themselves, or shall they go on a quest to try and find their lost guardians?

Elemental, Mephit

 Think of every hammy and cheesy sidekick to the villain from your favourite childhood cartoon. Now channel them all into a little imp with delusions of grandeur, and you got yourself a mephit. While all are true neutral, they are most often used by minions by other elementals and casters - and a good chunk of those your players will be encountering are certain to be evil. Bestiary 1 brings us four flavours - air, earth, fire, and water.

Ser Georgio D'Anunnzio the Third, Slayer of Beasts Large and small, is a brave air mephit knight. While he claims to be recruiting squires to help him slay a mighty cyclops, he has no real chance against the giant. Despite cooking for, cleaning after, and generally being subservient to his squires, he will still claim to be the leader of the band. If the cyclops is slain, he will also claim the kill - going so far as to challenge any false claims with a duel, although if the duel is accepted he is sure to flee.

Dirty Douglas is an earth mephit known in mage circles for being a highly effective assassin. The tiny murderer's method of operation is gliding through the earth to ambush the victim, tripping them to the ground, and then using a garrote to finish the job. Adventurers who slight the (easy to slight) Guild of Mages Supreme might end up having to deal with him.

The Song of Waves and Pyres is an annual event held in the neutral astral plane city of Foreverspyre. The ancient tradition dates back to when the planes of Water and Earth were in open conflict - but nowadays, a symbolic arena battle for prestige takes place instead. The only participants on both side are respective planes' mephits - and both groups are notoriously good at cheating. Fire mephits usually resort to hidden evocation scrolls and an occasional infernal pact, while water mephits' favourite tactic is to recruit other outsiders and even mortals, using magic to disguise them.

Elemental, Fire

 The fire elementals are so inspiring, that this writeup is already longer then their description in the book. Still, the actual stat blocks actually give us some fun stuff to work with - those stat blocks including the cinder rat, elemental inferno, living wildfire and salamander.

Space pirates of the Nebulon Reach use conjured cinder rats to efficiently sabotage enemy ships. Cinder rats are conjured right into the ventilation systems of space-faring vessels, and their fetid fumes, while not overly toxic, replace fresh air overtime. Some spaceships have taken to hiring teams of halflings, gnome and other small races - these teams are trained to squeeze into the vents and fight the extraplanar vermin.

Unlike other creatures of elemental fire, salamanders can't actually see through thick smoke. This can be very useful to planar travelers, who can sometimes bribe elemental wildfires or other sentient denizens of the plane of fire to help them hide their locations as they traverse the evil salamanders' domain.

Universitas Arcanum, the premier mage school, has a long list of forbidden summons for its conjuration class. While most creatures on the list made it there for their corruptive influence, the elemental inferno is on the list for a simpler reason - it's only purpose to exist is to burn and destroy. However, some younger, more radical mages are looking to challenge several rules of the institution, among them the inclusion of elemental infernos on the forbidden list - but for all their academic pedigree, the mages also feel they aren't good at debates, having spent their lives as reclusive hermits. They are now looking for a lawyer, or really anyone good with words, to take up their case with the high council

Elemental, Earth

This group of golem-lites includes the living landslide, sod hound, stone mauler, xorn, and elemental avalanche. They also need almost no introduction, as "behemoth made of earth and rubble" is just such a common trope across all media.

The Transrealm Shadowbank Corp is the largest chain of banks in the world(s), ran by a shadowy cabal of seven primal dragons. The dragons' rival has recruited several teams to strike at several of those banks, breaking their reputations as impenetrable. The easiest of those includes jumping through an unstable portal to a demiplane strongly aspected to earth - where gems are kept, and sod hounds alert their living landslide handlers when any single one of the precious stones is moved but a millimeter. 

A group of daring thieves have pulled off the impossible - managing to steal a precious diamond from one of the vaults of the Transrealm Shadowbank Corp. Unfortunately, just as they return to the material plane, closing the portal behind them, a hungry xorn appears, and with him some stone mauler thugs. The three-legged gem eater proposes a trade for the diamond, but his companions disposition clearly states that no is not an answer.

Birkenbock mountain is home to a grumpy old elemental avalanche. Unknowingly, when old ladies living on its slopes talk about keeping quiet not to cause an avalanche, they aren't talking about natural avalanches - instead, Ol' Slide is particularly fond of his peace and quiet. Those in the know will sometimes leave offerings in the form of scrolls of silence or similar magical trinkets, and just sometimes, they might unexpectedly stumble upon a gem, or a hidden cave filled with treasures, when traversing the mount.

Elemental, Air

 And so, our week of elementals begins, with the air elementals - including the elemental hurricane, invisible stalker, living whirlwind, the mighty storm lord, and the zephyr hawk.

Griefholme, the city of light and magic, is a place where magic is so commonplace that day-to-day life of most citizens relies on it. One of the many unconventional uses of conjuration is a bounded elemental hurricane that is let out into the streets at night - doing a job of hundreds of servants with brooms within mere minutes. While the creature is under strict orders never to initiate a fight unprovoked, it has taken to its duty very seriously, and will aggressively defend the hygiene of the city.

Whisper is an invisible stalker with a vendetta. Having been called to perform terrible deeds by a rogue necromancer one too many times, he plans to execute the mage. To that end, he has given the necromancer the location of some ancient treasure, hidden on a solitary, faraway mountaintop - but also failed to mention that said mountaintop is an elemental vortex point, notable for being the spawning grounds of large numbers of aggressive young living whirlwinds. However, Ol' Joe the Necromancer wouldn't risk his own life - instead sending naive young adventurers after the treasure, with promises of rewards sure to be broken.

Hush Featherstep is an ancient storm lord noble. In his youth, hush was an avid falconer in his home plane of air - and even in his old days, his trustiest companion, a zephyr hawk named Swyft, had been at his side. Unfortunately, these days Hush's sight has grown weak - and when Swyft goes missing while on a hunt on the material plane, Hush must turn to some mortals for help. All of the signs point towards the bird-like elemental flying straight into a massive storm brewing on the horizon.

Elananx

 Hey, what if the Cheshire Cat wanted to murder you? And also became an arsonist along the way?

While most elananxes, due to their inherent fey arrogance, avoid goblins, the goblins instead adore the fiery cats. The Burning Bowel goblin clan indeed managed to tame some several generations ago, and have since had a semi-successful breeding program. The goblin-bred elananxes may appear malnourished, but in addition to their fiery attacks, many of them carry the same diseases that are usually present on goblin dogs that they replaced. Although several fatalities happen when brave goblins try mounting the proud felines, the spread of arson and mayhem works out for both parties.

Mad Morgan the Firestarter is a sadistic arsonist wanted dead or alive in seven different kingdoms and thirteen duchies. While Morgan himself is a scrawny, cowardly man who can't really hold his own in a fight, an elananx has decided to follow him. The feline creature has a weird sense of adoration for the old criminal, and while it mostly follows along to bathe in the fires the man starts, it shows a level of loyalty in defending him few of its kind are capable of.

While elananxes are violent and attracted to destructive forces, they are still fey, and signs of adoration will sometimes stay their hand. Indeed, the elananx pack of Bluebloom forest have developed a strange affection for honey harvested from the giant bees that dwell in the Hintari Highlands. Offering the pack's leader (usually the quickest, most slender female of the bunch) a jar of said honey will not only get travelers safe passage, but the fickle feline will also give them three strands of their hair. These hairs each have a different effect when activated by throwing them into the wind. The first shall make the user invisible. The second, let them fly like a wind. The last one shall grant aid from an unexpected source, but once it has been used up, the pact is over, and the elananxes are free to hunt once more.

Efreet

While i kind of hate the "hehe, every wish gets corrupted" trope that seems so popular in the hobby, and even consider it a symptom of a greater issue - namely, the players vs GM mentality - if you really like those? Use Efreeti, its implicitly in their nature to corrupt wishes to their own gains.

Aggagni the malik has a very specific choice of victims. His army of spies, scouts and turncoats is present across the world. Whenever a sorcerer with a fiery blood, someone aspected to a fire breathing dragon, or a cleric worshiping one of the fire gods makes their first kill, Aggagni appears before them offering to fulfill a single wish. While he will rarely straight up corrupt the wish (unless insulted during the exchange), if a wish can somehow help him advance the construction of his fortress-city, he will take the opportunity. Once Granjipoor, the scourge of Mortals is complete, Aggagni plans to launch a full-scale invasion of the material realm and crown himself its god-emperor.

An immortal monster from the realms beyond is ravaging the world. Only magic as powerful as the wish spells can even allow it to die, though it would still take a heroic deed to actually slay it. The gods have abandoned the mortals, as they gave up hope long ago. As a group of warriors and mages prepare for their last stand against the foul beast, a devil and an efreet appear before them. The devil offers them a wish in exchange for their souls. The efreet smiles from ear to ear and says he will grant them a wish that will to exactly as they ask. As the sounds of wanton destruction draw ever closer, the heroes must choose.

Even without the wishes and fireballs, an efreet is a tough combatant. An efreet rogue's favourite way to loot is an overly elaborate prank. Several years ago, he decided to put an alarm spell on an ornate old lamp. When someone touches the lamp, the efreet dimension doors to appear before them, using some smoke and mirrors tricks to make sure the finder believes he was truly stuck in the inanimate object. If the victim is alone, he slays them outright and takes their belongings - but he much prefers meeting groups. In such a case, he spends a few days filling the ears of the finder (his faux "master") with tales of jealousy and betrayal - and when the group inevitably starts a fight, he uses it to disappear with their treasures, as well as the lamp. Then he places the lamp somewhere for the next poor suckers to find, and the cycle starts anew.

Eel

 While the electric and giant moray eels share a basic form, and an ability to slowly move on land, these are otherwise quite different critters.

The annual dwarven Highland games include many, many feats of strength and endurance. One of them is a race through a knee-high muddy pond crawling with electric eels. While serious injuries are rare, folks falling face-down and rolling over each other in the mud are expected, and treated with jest.
The winner traditionally gets a thunder-infused weapon, as well as a hearty eel soup.

A sea hag who often bargains with pirates resides in a cave accessible only by diving beneath the waves. While the cavern is by no means hard to reach, especially during low tide, a moray eel decided to lair at it's very mouth. What should have been a simple dive now becomes a deadly encounter, especially for those who come unprepared and are ambushed by the dread creature.

Junkeep is the capital of a newly formed goblin kingdom. The stinky keep, built out of incredible amounts of scrap material, is also surrounded by a moat that also serves as a sewer. In that filth-ridden liquid resides the royal alchemist's greatest achievement - a huge moray eel that also has the electricity-producing glands of its smaller cousins. While it has an aversion to goblin meat, the creature has been known to crawl out of the water and attack the city's few guests on occasion.

Eagle

 Whew, another letter down! On to some simpler encounters, i bring you the eagle, along with the tolkienean giant eagle.

The Everfyre planes are the territory of The Great Eagles. While the majestic birds don't have anything resembling a state, and their ruling body is naught more but a council of elders, it's has been a long-standing custom to ask their permission before settling in their lands, or even more rarely, collecting resources there.
Greedy King Glabradox, unfortunately, stepped all over said tradition and set up several logging operations across the region. These days, any humanoids that trespass without a heavily armed escort are snatched taken to the eagles' home, the Lonely Mountain, for interrogation.

The great eagles of Crownspire train hunting birds for the elves who live in the woods below. However, the eagles are not above intrigue and subterfuge, and more than one falcon has stolen an amulet, hid a letter, or outright attacked their master. When an elven noble ends up dead, their eyes pecked out, an investigation is called for.

The great eagles of Uplands betrayed the ancient oath that they made, and disaster struck. Long ago, the first bird-king made an oath that no kin of his shall ever take part in land-walkers' wars. And yet, the Dark Lord's advance was a threat to the entire world, and so the Eagles flew to war. Their aid turned the tide, and the Dark Lord was defeated once and for all. The day after he fell, the first Eagle lost his mind. In the weeks since, every day the great birds have been going feral. The eagles' now ask the mammals to return the favour - namely, by seeking out Mother Cassowary, a living deity that resides in a land no Eagle is allowed to visit, and petitioning her to lift the curse.

Duskwalker ghost hunter

 Duskwalkers are the spawn of monitors/psychopomps and mortals, and thus deal with matters of life and death - though their mortal nature might make them fare more prone to making mistakes.

A duskwalker tracks down the party, claiming he is a ghost hunter, and senses the taint of undeath in the camp. Apparently, one of the party members is a vampire who cheated death, but has been hiding that from the rest.
In truth, the newcomer is no ghost hunter at all - he is a charlatan, hired by the group's adversary, hired to create tension and distrust, and make them easier targets.

In the world of Scythar, duskwalkers are the only beings on the material plane able to see ghosts and spirits. However, after a bloody civil war, they are now treated as a lesser race, and are hunted down.
The Guardians, an order of champions dedicated to protecting the world from supernatural threats, have heard a prophecy foretelling the advance of an entire army of spirits coming to eat the mortals' souls - but fighting such a threat without the aid of the duskwalkers spiritsense is nigh impossible. Regrettably, even those few among the monitor-kin who would be willing to help mankind have retreated into unknown sanctuaries, and just finding one is a tremendous task unto itself.

Though most duskwalkers hunt for restless spirits, some utilize their talents differently. Wahrong Whitehair styles himself a businessman and a patron of explorers, champions and heroes. In truth, his trade is tracking down the restless dead - and then selling their locations and (for an additional fee) secrets and weaknesses to would-be heroes.