Pathfinder : Mana burned
The Shadowfell is the plane that encompasses the core of Merin. The underground passages that spread out under the ground eventually lead to things called shadow portals. They are natural places that signify the change between The Material and Shadowfell. While Shadowfell is not technically it’s own plane but rather a plane within another, it is still not quite the same as the Material. First off the main difference is light. Light is considered a resource there, because fire is incredibly dangerous in Shadowfell natural light is hard to come by. Light is also more or less a luxury plants grow without here and light while making it easier to see is unneeded for eye sight. Creatures with Darkvision see slightly better in Shadowfell, but other than that only creatures native to the plane see very well. The color spectrum is replaced with what is referred to as the gray, which is self explaining everything appears in shades of gray. Because of this depth which is also just seen as lighter shades of gray takes years to get used to. The Shadowfell is full of dangers, many powerful creatures use it as a way to go unnoticed throughout Merin. Their are hardly any creature native to the plane, but many creatures have been warped through generations living on it. The most prominent dangers of the shadowfell around Seylon are The illithids. They control most of the areas underneath seylon besides two of note which they are constantly feuding with. A beholder colony under the Sands, and the area underneath and around the Dead Lands where a Lich priest of Vlare is gaining influence for his God in Shadowfell.