The Underdark
The Underdark is the vast network of underground caverns and tunnels underneath the surface of the world. Because of its enormous size and the intermixing of layers, it can be difficult to map and even more difficult to navigate. Switchbacks, drops, dead ends and miles of endless dark can mean death for all but the most capable navigator.
The labyrinth of tunnels is deeper than almost any surface dweller realizes, with passages leading miles into the mantel and to the very center of the world, where unspeakable horrors lie. The Underdark is not one giant cavern, but rather, many huge networks of caverns and caves. As a result, it was not always possible to travel from one end of the Underdark to the other without descending to a lower level, or sometimes requiring a journey to the surface before returning underground.
While surface dwellers frequently call the entire area beneath them "the Underdark", it is largely divided into several layers that are mostly distinguished by depth. While it was possible to travel from one place to another within a layer, the different depths tended to have few passages linking them.
Upperdark
Middledark
Lowerdark
• Areas suffused with Faerzress are always filled with dim light.
• A creature in an area suffused with Faerzress has advantage on saving throws against any divination spells. If a divination spell doesn't allow a saving throw, the caster must succeed on a DC 15 Constitution saving throw to cast the spell. Failing this save means the spell is wasted and has no effect.
• Any creature attempting to teleport into, within, or out of a Faerzress infused area must succeed on a DC l5 Constitution saving throw. On a failed save, the creature takes 1d10 force damage and the teleportation attempt fails. Even if the save succeeds, the teleportation attempt can suffer a mishap as if the destination was known only by description, regardless of how familiar the destination actually is. See the table in the teleport spell for more information.
Faerzress
An unusual magical energy the drow call faerzress pervades much of the Underdark. The origin of this mysterious arcane power is unknown. Legend claims it is an ancient elven magic dating back to the time when the dark elves were first exiled from the world above, but this is purely speculation. The drow and other Underdark creatures use the properties of areas suffused with Faerzress to protect their settlements. Areas suffused with faerzress can range in size from a few dozen feet across to several miles in diameter, and feature the following effects:• Areas suffused with Faerzress are always filled with dim light.
• A creature in an area suffused with Faerzress has advantage on saving throws against any divination spells. If a divination spell doesn't allow a saving throw, the caster must succeed on a DC 15 Constitution saving throw to cast the spell. Failing this save means the spell is wasted and has no effect.
• Any creature attempting to teleport into, within, or out of a Faerzress infused area must succeed on a DC l5 Constitution saving throw. On a failed save, the creature takes 1d10 force damage and the teleportation attempt fails. Even if the save succeeds, the teleportation attempt can suffer a mishap as if the destination was known only by description, regardless of how familiar the destination actually is. See the table in the teleport spell for more information.
Type
Underground / Subterranean
Included Locations
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