DMM Features

Architecture

Undermountain is made up of a mixture of smooth, worked stone and rough-hewn stone, with the occasional intruding natural tunnel or cavern. A few levels have exceptional architectural features.

Ceilings
It’s helpful to know the height of a ceiling, particularly if creatures in the area can climb or fly.

• Rooms. A room’s ceiling is at least as high as the room is wide, often higher. If a room’s ceiling height isn’t specified in the text, assume it’s the minimum height.
• Tunnels. A tunnel’s ceiling is as high as the tunnel is wide, unless otherwise noted. Most tunnels in Undermountain are arched and have no visible structural supports. Exceptions are called out in the text.

Doors and Secret Doors
Normal doors (including double doors) are made of thick, sturdy wood fitted with iron hinges and handles, and protected against moisture by magic.

Secret doors are fashioned of the same material as the surface in which they’re set (usually stone) and require a successful DC 20 Wisdom (Perception) check to locate, unless noted otherwise. When they are closed, most doors and secret doors create airtight seals, keeping gases and gaseous creatures from passing through them; exceptions are noted in the text.

A one-way door can be manually opened only from one side (the other side has no handle or hinges). A knock spell or similar magic is needed to open a one-way door from the “wrong” side.

Not many doors in Undermountain have locks, but those that do sport locks of masterful craftsmanship. When confronted by a locked door, a character with thieves’ tools can pick the lock with a successful DC 20 Dexterity check.

A locked or stuck door can be forced open with a successful DC 20 Strength (Athletics) check. A creature that fails a check to force open a door can’t make another attempt on the same door unless it has another creature or a tool (such as a crowbar) to assist.

If the direction in which a door opens becomes important, it always opens in.

Illumination
Since the creatures that originally carved out Undermountain had darkvision and Halaster lights his way by using magic, areas of the dungeon are unlit unless otherwise noted.

Alterations to Magic
To be determined upon discovery...

Elder Runes
To be determined upon discovery...

Gates
To be determined upon discovery...

Random Encounters
The DM checks for a random encounter once every hour, once every 4 to 8 hours, or once during the day and once during a long rest - whatever makes the most sense based on how active the area is.

The DM rolls a d20. On a result of 18 or higher, a wandering encounter occurs. Each floor has specific wandering encounters that can be introduced.