The Fade

A supernatural phenomena that encompasses the region between Shudan and Nobumori. Spending more than a couple of hours inside it causes permanent injury and eventually death.

Appearance and Effects

The Fade is not actually visible and continues to grow slowly over time, which makes it difficult to track the exact location of it's borders. Once inside however, it becomes immediately noticeable.
Creatures inside notice an immediate dimming of their surroundings as their vision becomes less sharp. Headaches and joint pains set in within minutes, and grows stronger as exposure continues. After a few hours, fatigue and muscle soreness grows, along with tunnel vision, and color fades to black and white. The name Fade is derived from this effect. Everything up to this point is reversible, and creatures that leave and spend days or weeks outside of the Fade usually make a full recovery. After this point, effects become more permanent.
Creatures that stay inside for more than 12 hours will start to feel deceptively better as the pain and fatigue eases and numbness sets in instead. Within a few more hours, walking becomes impossible and eyesight is lost completely. Death usually sets in before the 24 hour mark.

History

Shudan was founded by the Hotsukai and was populated and run by powerful arcane practitioners since it's earliest days. However, in H243, following the events of The Break, people's faith in magic began to waver. To make matters worse, conflict broke out between Shudan their neighbors to the east in the Nobumori.
Admid the growing instability, revolts began to erupt within Zonyashi and the Hotsukai became the target of an assassination attempt. Although he was able to defend himself, the instability of magic caused by The Break created a backlash that destroyed much of his keep and a portion of Zonyashi in the process. People began to look at magic users with distrust, and in small towns throughout Shudan they started to become pariahs.
In H254, in an effort to quell hostilities on their eastern border and restore faith in magic, the Hotsukai traveled to the border between Shudan and Nobumori himself. As his scouts had reported, there was a pocket of particularly dense Mana there. He attempted to use this to his advantage to create a temporary barrier between Shudan and Nobumori to slow the fighting and prevent an all out war. The backlash exploded out of control and wiped out hundreds on both sides of the barrier as well as the Hotsukai himself. This event, referred to as The Schism, was the birth of the Fade.

Although the original extend of the the Fade was not large enough to block travel between Shudan and Nobumori entirely, it was destructive enough and unfamiliar enough that both sides began pulling away quickly. In the years that followed, the yokai of the Nobumori retreated almost entirely into the forest and became isolationists.
In S1, Ono the Eastwind assumed leadership of Shudan and founded the Shudan Shogunate. The country was roughly divided into four parts, leaving the Eastern Province and therefore the Fade, under the supervision of the Hisashi Clan. In the years that followed, they failed to notice or simply failed to report, that the Fade was steadily growing.
In S89 this fact was discovered by Kanagi Remingale when he was forced to order the abandonment of Hokuya as it was being slowly overtaken by the Fade's growth. This kicked off a slow migration away from the eastern cities of Shudan towards the center, leaving the Hisashi clan in a tight position with regards to both their reputation and finances.

In S234 Mythea of the Cobalt Scar set off from Sukorak and began an extensive trip around the northern tip of the Fade to survey and map out it's growth over the past two centuries. During this trip she discovered that the Fade had not expanded as far into the Nobumori as it had in other directions, kicking off a series of experiments led by both her and Silia Lai.

The two discovered that consuming life, such as the trees of the Nobumori forest, slowed the growth of the Fade. This led to a massive effort to grow trees all along the eastern border of Shudan, starting in S238. Hatomi Remingale sent large numbers of Ironbound to help, and the four clans all contributed people as well. Silia's top students, Mitsugu Atsutane and Eden Morningfire, studied with some of the few druids in Shudan at the time to learn what they could about growing trees magically. Eden was able to devise some techniques that even wizards could replicate, and both he and Mitsugu spent almost a year on the eastern border teaching them to as many people as possible.

Although neither Silia nor Mythea were able to figure out how to entirely stop or reverse the growth of the fade, the decades since their effort has proved that they were at least successful in slowing it down.