Lost Lands

Introduction

The problem with magic is that there can bee too much of it, and when that happens, the world and its inhabitants suffer greatly. The more ambient mana in the environment, the more magical the animals are, the more likely the supernatural is to be encountered (and even to become the mundane), and the more the spacetime continuum itself begins to bend under the strain. Sometimes even crack.
By the time the Grand Empire of Karadia was born, entire regions of the world has effectively collapsed into a state where rules of the natural science apply occassionally at best, never at worst.
Someimes it resulted from the specifics of the regional cosmology that filled their world with so many supernatural creatures and phenomena that the locals can no longer tell what is natural and what isn't. Examples of this category include the subcontinent of Ind, the Golden Kingdoms in the central Arrica and Nippon in the far east).
Sometimes it resulted from a terrific magical disaster or a terrible war that decimated it completely while unleashing so much magic that it has completely corrupted everything in the vicinity. Here an example is the southwest continent of Menoria, southeastern continent of Drakka, and in more recent times, large swathes of Karadia in the aftermath of the Twilight War, during the effect commonly referred to as the Shattering.
Sometimes, however, there is no clear answer as to why some place just stops making sense.

Lost Lands

Summary

All such overtly mana-influenced environments are called the Lost Lands in the Grand Empire, a name referring to how those lands are effectively lost to the Prime Physical World, instead existing in a fundamentally different state. However, the foreign cases of it - such as the ones of Ind or Golden Kingdoms - are only referred to that way by scholars, as for majority of the inhabitants of the Grand Empire it's just what they are. A mysterious foreign land of many tales describing their wonders and terrors, who might or might not be correct.
As a result, when asked what the 'Lost Lands' are, majority of the inhabitants of Karadia will point towards the ones that are common to their land - entire regions of the continent warped by the damages of the Twilight War or the ones of even more unnatural origin. The former is a category that is much more common but much less valuable, at least usually.

Agri Deserti

Despite the horrid casualties that the Grand Empire of Karadia suffered, it would have recovered from them long ago if not for the damage to the very fabric of reality that accompanied them. At some point, soon after the end of the war, it is estimated that 97% of the Karadian territory classified as the Lost Lands (or, to go by their local term, the Agri Deserti), their very geography no longer making any sense.
Mountains, rivers and forests seemingly moving from one place to another overnight. Islands or regions that once were a hundred mile wide now being thousand or tens of thousand of miles wide and filled with pure chaos. The level of ambient mana of those regions has also grown, making it much more common for random spirits to not only appear there but also stay.
During the first century after the Twilight War, the Grand Empire managed to retake large swathes of its own territory, using leftover pre-Twilight War techmaturgy to stabilize them back into conventional reality, although one usually very different from what it once was and often much larger or smaller than it should be. But it never recovered everything, far from it in fact.
The parts of Karadian territory that remained the agri deserti was usually seized by the followers of the Hierarchs or by other groups hostile to the Grand Empire, such as the WIld Courts. Further recovery efforts become a standstill, with the Grand Empire unable to push forward aside from some rare cases usually caused by the in-fighting among the inhabitants of those Lost Lands that left them weakened and exposed.
The interesting part is their existence has become a somewhat mundane fact of life to most. Usually, they're just a very large scale cases of 'larger on the inside' with higher than usual amount of supernatural prowling around, far from being genuinely dangerous. Yes, they are hard to navigate due to most maps remaining valid for days at best, but other than that, they just are. Many are even actually controlled by the Grand Empire, yet not stabilized because it would cost resources that are scarce, and wouldn't really change anything for the better.
Of course, there are also regions that are sliding further and further away from the rules of the Physical Worlds, divided between holdouts of various supernatural forces with powerful creatures in charge of them that has imprinted themselves on the somewhat mana-enhanced environment surrounding them, warping it to be more to their liking.
It is estimated that while more than 50% of Karadia was successfully stabilized and no longer counts as the agri deserti, the Grand Empire-controlled territory is still fifteen to fifty times smaller than the area left to be recovered. This is due to the remaining agri deserti usually including the areas where the reality was most warped, resulting in them being much larger on the inside than they are when seen from outside.

Magical Anomalies

The other category of the Lost Lands as intimately known to the inhabitants of Karadia are the places that are wrong, despite there being no clear cause for that. It is, however, a category that's known mostly to the scholars, as for adventurers and the people living closeby to them, there's a little difference between those and the agri deserti, even if there are clear mechanical differences.
Magical anomalies are usually much more alien than the agri deserti for a simple reason - most of them are born due to Prime Physical World (and its local cosmology) coming into contact with another world, with the foreign magic flooding inside this universe and being converted into something more compatible with the laws and rules of the local cosmology.
They are fairly rare, and often the difference between them and the most alien parts of the agri deserti is very muddled, especially when Pentagram and forces of the Umbral Bond are involved.

Dungeons

A relatively rare thing only encountered within the territory of the Karadian cosmology that will be described in detail elsewhere. What has to be mentioned here is that they, too, are a form of a Lost Lands, however one created artificially and under perfect control of its designated overlord, the Dungeon Lord - who within their domain is pretty much a god.
Who exactly created them and why is something that's up to a religious debate. However, they are generally considered to be the least dangerous among the three main types of the Lost Lands within Karadia, and often used as training zone for the adventurers before they enter agri deserti or a magical anomaly - at least the smaller ones, as the larger ones can potentially reach the level of value and difficulty of the most terrible of magical anomalies and the deepest recesses of the agri deserti.

Geography

The geography of the Lost Lands doesn't make sense. That has to be said at the very beginning. The reason why some scholars consider their existence the proof of the Prime Material World approaching transition into a Spiritual World is because - to a degree - the rules of the Lost Lands have more to do with the rules of a narration than of cold, hard science. To actually understand those rules and know how to use them for your advantage is the key part of any adventurers' training.
To begin with, the shattered reality of the Lost Lands operates on several levels. The first level can be described as 'large geographical features'. So mountain ranges, really large forests, great lakes, plains etc. Such locations remain relatively consistent, however the same can't be said about their finer details, who make for the second level. The smaller (and less notable) the feature the less likely they are to remain stable.
For example the mountains in a mountain range will remain more or less consistent in their placement, however you can expect their exact size to change (rarely the height changes more than few hundred meters), the details of their surface will certainly change, and they might occasionally venture in either direction for few dozen or few hundred meters. However forests - whose 'composite elements' are way smaller, will change rapidly.
The exact placement of trees will change almost at any given moment (sometimes needing only a few minutes without anyone looking), although the larger elements (such as a not particularly deep ravine blocking your party's way) will remain slightly more consistent. The edge of the forest will stay in more or less the same place, but when you camp right at it, you can expect the trees next to your camp to change their placement. Which greatly builds up the paranoia.
The third level of reality are places and things that are anchored to a stable reality. This is especially pronounced in things that are long and narrow, such as roads and rivers. If there is a road constructed in the agri deserti between two enclaves of stable reality, it will be only partially altered by the reality-twisting nature of this place. In short, while details of the road itself (such as where exactly it goes through, and to a small degree its length) might change, it will continue to connect two enclaves of the stable reality. Even if its damaged somewhere, it will remain a 'road connecting two places but is damaged' on a narrative level, and that will maintain the connection.
Some scholars speculate that the details of the road/river/something else are only changing because other geographic elements are 'pushing' them with their drift. Of course, even then, the creation go such an anchored road isn't easy. Such attempts are extremely vulnerable while on their assembly stage - a large group of workers and armed people placed at the now expanded 'end' of it is enough to temporarily anchor it (it's, once again, a bit of a narrative thing, with such groups departing from stable lands and drawing a line through the agri deserti meaning that the start of this line is where they started from), however if there is an attack on such a group the anchor can be easily destroyed and then there is a large chance of the road simply vanishing.
The fourth level is the conscious alteration of the agri deserti done by sufficiently powerful entities. Supernatural entities on the level of at least archdaemon are capable of causing what's called imprint - a large scale alteration of the agri deserti, centered on themselves (although if they stayed somewhere for a while, their imprint will stay for a while if they will leave the domain temporarily). The archdaemon-grade imprint typically requires some constrained space, so a cave system, a ruined outpost, a grove in the forest or something similar.
Imprint not only passively warps the reality to better suit the master's nature (so for example expect a lot of death mana in a ruined castle's dungeon inhabited by a Breathless Tide's archdaemon), but also allows them to a degree to warp the reality consciously. Archdaemon can easily mold or even expand a cave system they moved into, fill it with traps and servants and so on. Even some particularly powerful mages (especially archmages) are capable of similar alterations in non-imprinted territory, but without daemon's ability to mentally multitask for decades if needed, they will quickly tire or lose concentration.
The much more powerful demigod-level imprint is rarely restrained to such locations. It's typically divided between the active and passive imprint zones. Closer to their seat of power, the demigods are capable of making any alterations they wish, on a power level far surpassing the archdaemon imprint - they are demigods out there whose active zone is approaching a dozen square kilometers. The passive zone can be ten times larger (although it's normally smaller than that). It lacks the ability to make conscious alterations, and the demigod behind it will not be acurately aware of everything that's happening there.
However there will still be notable changes, including alterations of aesthetics (for example a forest within a passive imprint zone of a Breathless Tide's demigod will wither - until the ruler is slain, and something else moves in, which is when it will rejuvenate entirely within few days) and spawn of creatures aligned with the ruler's nature. So undead for the Tide, abominations for the Rampant Bloom, etc. An archdaemon can settle their lair within such an imprint zone too - they can regionally overwhelm the passive imprint zone without alerting the demigod. Which is a bit risky, since demigods tend to consider their passive imprint zone to be a part of their domain too and might react badly to such invasions (then again, many simply doesn't care).
It has to also be noted that the shape of the active and passive imprints follows narrative logic. If a Wild Lord of the Wild Courts moves into the center of a forest that's somewhat elongated, the imprint will overtake the forest (to a reasonable distance from the seat of his power), but will most likely not expand outwards, for as long as the forest is sensibly large - as a result, what's a five kilometer long zone in one direction might only be one kilometer long in another (however to actually reach and penetrate the active zone surrounding the demigod in order to assail him is enough of a feat, even when it's 'only' one kilometer).
The fifth level of the Lost Lands can be called 'disturbances'. The Reality in the agri deserti occasionally doesn't make sense even more than normally. A demigod or an archdaemon can warp reality beyond the borders of imprint, in order to make their domains harder to access - leading to a situation where for example submerging yourself in a lake will make you emerge in a completely different version of the forest surrounding it, one being the domain of a demigod that decided to get creative. Sometimes a road suddenly gets an intersection, with the newly appearing road leading to a lair of something that wants its food to get to them on their own.
Sometimes a demigod or an archdaemon decides to alter their surrounding so much that it completely stops making sense - for example imagine a ruins in a middle of the swamp. You get down the stairs, walk through an underground corridor - and after opening a gateway you are suddenly on a grassy plain. There are also cases of some completely external, even extrauniversal influences overlapping over entire region of the agri deserti, and causing some changes to their area of influence. In the end, disturbances are almost always caused by 'something', and tend to be a high risk high reward affair for the adventurers.

Ecosystem

The 'background' of all the imprint zones and so on of the Lost Lands are typically the fae, animals and beasts - they tend to be anywhere, and have become part of the very fabric of the Lost Lands to the point to the point when they are often influenced by imprints. This is especially common in case of the fae, with their wild brethren living outside of the Wild Courts's domains often treated as a mine canaries - if they start changing somewhat, it means that something in the Lost Lands themselves changed and is now influencing the wild fae.
This means that majority of the Lost Lands are in fact composed of a relatively stable ecosystem, similar to the outside. It is however expanded upon - there are beasts, sometimes truly grand in size, there are also the fae (some of which are pretty much a more magical part of the ecosystem).

Localized Phenomena

The changes to the world isn't limited to the terrain - the weather and even the sky is also affected. Storms and other weather phenomena in this world generally tend to be grander than the ones on Earth (due to the world being slightly larger as a whole), however the Lost Lands put the whole system into further disarray by adding a lot of magic into the mix. The climate in the Lost Lands can sometimes not make sense at all - there are areas of perpetual winter or jungles so far north, only because the local Wild Lord wanted it like that.
The passive imprint zone of a demigod can influence the weather by adding special phenomena with no relation to anything that's happening outside of the Lost Lands. For example demigods of the Nine Hordes are known for often causing the ragestorms - the storm-equivalent during which the blood is raining from the skies, and anger overtakes all but those with the most willpower. Sometimes such created phenomena can expand beyond the borders of the domain.
The even higher level of phenomena are the ones concerning the skies. The sun, moons and stars visible in the Lost Lands are false ones. In fact, many suspect especially the stars to be a reflection of the other worlds (meaning that every star our there is in fact a separate universe, either Spiritual or a Material World that's somewhat making itself visible in the Prime Material World). This means that any astronomic phenomena in the Lost Lands is not only extremely magical, but will also cause wide-scale alteration of entirety of the Lost Lands (at least for the time being).
This includes both phenomena that are relatively familiar to inhabitants of this world (such as the solar eclipse causing massive empowerment of the forces of the Shadowlight Covenant) and those that are unknown outside of the Lost Lands (such as the dreaded blood moon, which is when all forces of the hierarchs are empowered and tend to go on a rampage, or the voidwave during which all stars vanish from the skies and looking at the now-empty skies during the night threatens your sanity - while empowering the forces of the Pentagram).

Natural Resources

While the Lost Lands are the dreaded phenomena in the Grand Empire, they are not without its own share of beneficial effects. They are a literally inexhaustible wells of resources for the ailing imperial industry. The magical energies of this place cause many plants and minerals to gain potent alchemical properties. The same can be said about the (once again, literally inexhaustible) supply of beasts, that offer leather, meat, bones and numerous other crafting materials. Adventurers are often tasked with harvests of such materials, in fact it tends to be their main source of income.
Other minerals and metals that can be used in metalworking are similarly endless. The Grand Empire has actually established a number of mines in places where ores of strategic value (for example antegnite in the Valley of Ashes magical anomaly) were discovered, simply because for as long as the mine is not depleted, it cannot be depleted - this is where the narrative logic of the Lost Lands comes into play again, as the depleted mines stay depleted as their name says, however 'active' mines with resources will also stay like that.