Plane of Predation

[Insert Name here], The Plane of Predation

It's not a bad place to be, at first. The air is thick and humid, but not miserably so, at least not once you get used to it. It's often sunny, although at the same time there's a near constant light rain. Even the rain is sort of nice, though if you stand in it for any length of time your skin starts to feel uncomfortably raw.
The air smells sweet, but somewhat cloying. You get used to it, even the slight taste of acid it leaves on your tongue. It's so full of life that you really can watch plants grow, if you're patient. If you get a clear view of it, the horizon always seems to be in some state of barely-perceptible flux, like a heat haze slowed down a million times. You never get used to that.
It has breathtaking white, sandy beaches bordering sparkling waters full of things that will eat you. It has picturesque, winding rivers full of things that will eat you. It has gorgeous, awe-inspiring rainforests full of things that will eat you. Most of these things are intelligent and none of them chew.
And you can't get out.

Planar Traits
Objective Directional Gravity -The plane is on the inside of a massive, well not sphere, but certainly spheroid object, "down" is wherever the closest edge of the spheroid is
Normal Time
Self-Contained - Being inside a hollow spheroid the plane naturally loops back on itself
Alterable Morphic [Possibly with implications it's sentient, or at least alive]
Minor Positive-Dominant - All living things in this plane gain fast healing 2, though they lose this trait while exposed to the waters or rain of the plane, unless they're immune to acid damage
Mildly Neutral-Aligned
Normal Magic [Maybe something to boost plant affecting spells, acid spells, and/or druid spells?]
[Some sort of entrapping like effect to represent the SAN damage/increasingly predatory mindset of those who fall victime to the plane's corruption?]

Stories tell of a parasite plane, or perhaps it's some vast elderitch being, one that feeds off of the planes themselves, leeching materials, magic, and souls to keep itself running before some natural process of the worlds drive it off, portals into it are one way for the most part, pulling in places, objects, and people seemingly at random when it feeds, exits are much rarer, and could better be described as wounds created the few times something's managed to tear it's way out.
Internally it appears to be on the inside of a massive, hollow ...not quite a sphere, by certainly spheroid, locations within it shift and move, slowly but an observant explorer can note how it churns. The air is thick and humid, cloying fragrances to lure in prey from the plants and animals that call it home fill the air, but a strange, acidic taste will always be on your tongue. The dirt underfoot is the ground up remains of countless ruins and landscapes it's swallowed up, newer things half burred under the soil, twisting roots, and layers of flora, getting older and more torn apart the further you go down, That is if you can even find the ground, the whole plane is overflowing with strange and fantastic flora, some picked up as it fed off of other planes, some found nowhere else, some seeming to form the backbone of the plane itself, as they twist together in great landscapes.
And plants are not alone in this jungle, many many beasts call it home, some big enough to be mistaken for mountains, some smaller than your thumb, but an uncomfortably high number of them absolutely gigantic and each and every last one of them predatory in someway, most life here is, from the greatest beast to the smallest pixie, everything here is a predator to something, even the plants will seek to feed on the unwary. And most unsettling of all, much of it's inhabitants are sapient, nullifying the greatest advantage most mortal races have as the twisting vines of the jungle consumes any trace of civilization that can't fight back.
Humanoids are not the top of the food chain here, and would be wise to remember it


[Plane] Links

Most planar links into [Plane] are one way, sudden eruptions of color and motion snatching up the unsuspecting and dumping them somewhere in [Plane], leaving them at the mercy of the hungry jungle

[Plane] Inhabitants

Inhabitants of [Plane] can generally be divided into two categories survivors and natives
Survivors are those poor souls that have been dragged into [Plane] and have etched out some safe-haven, or at least the illusion of one, orcs and elves tend to be the most common of races from the material planes, though groups of humans, gnolls, lizardfolk, and other such tribal races are not infrequently seen. Survivors tend to be organized into tribal hierarchies and semi-nomadic bands, large enough to fend off most "small" predators of the jungle, but not big enough to attract the great beasts that normally wouldn't pursue human-sized prey. Many are hesitant and wary, slow to trust in this world of eat or be eaten, often clinging to any vestige of civilization that can be found here, at least until the jungle consumes it and likely them

Natives on the other hand are those who seem to fit right in with the plane, regardless if they've been here for countless generations, or only a few days. Typically staying in small groups or by themselves, they seem to relish the red in tooth and claw nature of [Plane], seeing little to no value in the trappings of civilization and becoming more and more like the beasts of [Plane] as the years go by
On an unsettling note, it's not uncommon for survivor tribes to fall apart when a number of their members start going a little feral...

Beasts of [Plane]

There are no true herbivores in [Plane], a number of creatures are omnivores but everything here will eat meat, even the plants. And many are large enough to see humans as little more then prey. A special note should beasts of [Plane], many, many of them are sapient and, if not able to converse with their prey should they chose, then at least having an unsettling glimmer of intelligence in their eyes. Pretty much anything large and predatory you could imagine stalking the shadows of a jungle can be found here, and quite a few you'll find no where else, great serpents, dinosaurs, large felines and more exotic things such as lamias and hydras abound, many of unnatural size and though exceptions always exist, how dangerous a beast is can generally be determined by it's size
Smaller than humans - Fairly rare and typically safe, though exceptions do exist such as [piranha faeries], these creatures are too small to actively prey on humans, though it's still unwise to give them the opportunity
Human sized and a bit above - You can drive them off if you’re well-armed, highly skilled, or both, by far the most common threat to survivor groups
The tier above that (the things that eat the things that eat humans) - Extremely dangerous. Run or hide. Fighting is a last resort, unless you’re incredibly well-prepared
The tier  above that is remarkably safe - They’re about as interested in humans as a Megalodon is interested in a lone sardine. (Don’t gather approach them in a group of any appreciable size, all you're doing is making it worth their while to hunt you) You can learn interesting things if you manage to engage one of these creatures in conversation, but doing so is risky; it might decide to eat you after all. (In general, remember that cordial discourse is not an indicator of friendliness on this plane. The thing you are talking to may simply be very confident that you aren’t getting away.)
The Hungry Gods - Whether they’re actually divine or not doesn't matter, they're so rare that nobody really knows how they behave, and nobody with any sense wants to find out. Accounts differ. They might ignore you. They might not.
The Apex- Don’t fuck with the Apex. Ever.

Features of [Plane]

>The Charybdis
All rivers in [plane] drain to it's sole sea [maybe name it?], and the sea drains into the Charybdis, a massive, churning vortex of water and wind draining the ocean and all that's caught within it and never giving anything back.Many who know of it's existence assume it to be some grand predator, large enough to sip the sea and disrupt the waters enough to cause what passes for tides in [plane], though a few brave souls believe it to be an exit, fewer still attempt to make their way to the bottom of it, either way they're never seen within [plane] again

>The Wound
If one somehow manages to dig past the ruins and the roots that fill soil of [plane], or simply digs where the crust is thin, one finds strange, almost fleshy fungal fibers mixed in with the dirt, getting thicker and more intertwined the deeper one goes, until eventually it becomes a solid wall of eldritch flesh, furthering the rumors that [plane] itself is a living creature and stymieing any further attempts to go deeper by being too thick to cut through, at least not without attracting the attention of burrowing predators. But...if the plane is alive and that is it's flesh, what happens if one cuts through? Could one escape this hungry jungle?
Rumor has it that in some place something cut through, stories are often conflicted as to where, often times hidden in deep mines and ruins or at the place where grand predators one battled, some even state there's more than one! Perhaps on more than one occasion something cut it's way out (or more worrying, in) and that's why the tales are so conflicted. But maybe there's another reason, maybe when one exists maybe it's only temporary, after all wounds heal

>Ruinsfield
There is a large area within [plane] where ruins pile on top of each other, architectural styles from many lands twisted and mixed together as the implacable motion of the plane grinds them against each other, was this once some final bastion of civilizations that got pulled in? A safe refuge where people lost to [plane] could seek shelter against the jungle? Who knows, the inhabitants are long gone, though the protective barrier surrounding the ruins are still intact albeit with a handful of monsters trapped inside

>The Apex
More myth than fact, god than beast, feature of the plane than actual monster, The Apex is the absolute top of the food chain. Some say it's the god that created this place, a realm where it could hunt for eternity, some say it's the embodiment of the plane itself, an immense creature, always hungry, some say it doesn't exist, either way all within [plane] fear it, and a few even idolize it


Monsters of [Plane] (Specific ideas)

>Pitcher plant siren
A large pitcher plant with a lure, the lure in the middle, the lure can cast things like charm person/monster and suggestion

>Saurian
Large, carnivorous dinosuar, not as big as some of the dinosaurs that stalk the jungle, but there's a disturbing intelligence in it's eyes, slightly smaller than a t-rex and will often set traps and use primitive weapons

>Long legged crocodile (needs a better name)
Large, bulky crocodile, though it stays in the water most of the time it's legs make it rather suited to chasing down prey on land

>Rock frog
Large frog, back covered in rock like growths making it blend in and providing natural armor, able to swallow a man whole, several infact

>Dragon sized bat (Needs a name)
Large predatory bat dwelling in the upper canopy

>Colorful Roc
Self explanatory

>Some sort of large, jaguar like cat
Self explanatory, needs a better name, probably sentient and may have displacer beast like abilities

>piranha faeries
Bright, colorful faeries, easily mistaken for a swarm of butterflies at a distance, individually safe, but in swarms act as a nasty little swarm of flying piranhas with glitter

>Laima treant
Large treant with a serpentine tail instead of legs, overall has a vaguely reptilian shape, can grow to be one of the largest predatory plants in this plane


Things I want to include but am not sure how/notes from other people's posts
>Corruption effect - Longer you're there the more the plane gets to you, whether from the constant stress or something more insidious, people who survive long enough tend to go native. They assimilate. There are two general theories as to why this happens. Some people think that the plane itself is alive, and slowly worms its way into the head of anyone who stays there too long. Other people attribute it to the accumulated stress of living there. Humans aren't rabbits, and in the long run they aren't equipped to handle the perpetual anxiety that comes with being prey. Maybe, the thinking goes, everyone eventually cracks under the pressure.
Either way, people who are stuck on the plane for a long time acquire strange tastes. Those who have been there far, far too long may come to think of it as a genuine paradise. And the idea of eating a sapient being as not that odd

>Psudoreligion - acceptance of the food chain than actual religion. Have the PCs notice a terrifying trend that if a true native of the plane is caught by something bigger than them they just stop. They don't cry, or fight, or scream, they just basically go limp and have no emotion as they accept "the way" of things. Even have the party's guide captured and simply stare at them as they meet their end. Not pleading or anything. Just acknowledgement that they are there. Possibly have that fall into the horrible things the plane does to your mind over extended periods of time. That could be a rather unsettling way to handle it, I like. Closest thing to resisting they may ever do is something like pray their time doesn't come today, instead of praying that it doesn't come, could act as a bit of foreshadowing too. Hell I could see a similar thing being why sapient predators seem so unconcerned about eating someone they just had a friendly chat with, everything has it's place, at times predator, at times prey, and it's pointless to fight against that

>The plane feeds on souls too - Some sort of psudoafterlife with the implication it's just a part of the plane/the plane isn't willing to give up ANYTHING it consumes, even the souls of those trapped in it, possibly an extra layer or two of the plane with a mockery of heaven/hell just as hungry as the 'material' layer of the plane