Heroes of Hillsfar
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.
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-suffused area must succeed on a DC 15 Constitution saving throw. On a failed save, the creature takes 5 (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.
- Areas suffused with faerzress have become tainted by the chaos of the demon lords. When a spell is cast in a faerzress-suffused area, the caster rolls a d20. On a roll of 1, the spell has an additional effect, determined by rolling on the Wild Magic Surge table in chapter 3, “Classes,” of the Player’s Handbook.
- Though faerzress can’t be dispelled, its effects are temporarily suppressed in the area of an antimagic field. Similarly, characters that take refuge in an extraplanar space (such as with Mordenkainen’s magnificent mansion) are not affected by faerzress. Other effects (such as Leomund’s tiny hut), however, do not provide this protection.