Shadowfell

The Shadowfell

Sometimes called a realm, it more accurately resembles pockets of darkness, with similar characteristics, on

the back of the prime material plane. Despite these similar characteristic, they do not share a geography but can be travelled between:

* One cannot teleport from the shadowfell into the prime material plane, though they can use the spell Gate, or plane shift to leave;
* Some areas of the shadowfell are parallel to their material geography (like in stranger things.silent hill), while in others they are the same, and the area is literally in the shadowfell;
* Entering the shadowfell requires spells (such as plane shift), a gate and key, being enveloped by the shadowmists, committing an act of evil near a gate,  or create an act of great great evil (which can create a shadowfell territory), or when willed by a ruler of the shadowfell lands;
* Leaving is much more difficult - plane shift, gates, wishes and such only work if no claim has been made on the would be escapee (i.e. they have not entered a pact, made a deal or drawn the attention of the dark powers either by being good or by committing acts of evil);
* Spells that allow travel to the ethereal plane, only allow movement to the border ethereal and leaving the ethereal plane, they are left back in the shadowfell;

Rules: The Shadowfell changes numerous rules

* Necromatic spells are more effective (+1 damage per dice for necrotic spells, resisting necromency spells have disadvantage), and undead are more powerful (lots of ways, some have more hit points, regeneration, get advantage in turning attempts)
* Paladins/Clerics -Detect Good and Evil - reduced in range to 10 ft
* Beings granted divine spells from Good powers, act as a beacon to the dark forces vying for power
* Committing evil and dark acts draws the attention of the dark lords, and ties beings to the realm permanently;
* Teleportation spells allow transportation within a realm, and between realms within the shadowfell, but never out of the shadowfell;
* The sun never fully rises in the shadowfell, it is always obscured by clouds, fog, even when there is full light, it is never considered sunlight
* Each realm has unique features and environmental rules;
* As people spend time in the shadowfell, their memory and knowledge of the world they were in before the shadowfell begins to fade.

Spells

A number of spells have minor changes:

* Alarm - instead of beeping or pinging, the triggered alarm is a bloodcurdling scream;
* Mage hand/Bigbys hand: the congured hands are skeletal;
* Find familiar, find steed, phantom steed: summons a skeletal animal, immune to turning;
* Fog Cloud (and any version of it); the fog has harmless grasping hands appear in it;
* Gust of Wind - moaning is heard;
* Any spell that summons a pocket dimension - inside it hears crying and screaming;
* Maze, wall - has ghastly faces carved into it or moving in it;
* Telepathic bond, contact other plane - you feel like someone is listening into you;
* Revivify - a creature restored to life, wakes up screaming;
* Spirit guardians - appear skeletal
* Any resurrection, reincarnation spell, along with other side effects wakes up with some sort of madness;