The Lands of Deepearth are presented in detail as a setting that
you can use for your underground campaign. The known varieties
of intelligent life each claim a portion as their own, and a
group of PCs can gain many levels and overcome
towering obstacles, without exploring Deepearth in its entirety.
If you prefer, regard the lands as an example of the underground
ecosystem and its many components. Utilize those
aspects you like in your own campaign, and disregard others.
Expand this area as much as you wish-as presented, the realms
of Deepearth occupy no more area than a moderately small
nation. Certainly there is potential for many such underground
realms under the lands and seas of the fantasy world.

The realms of Deepearth are mapped on the following pages
for your easy reference. Each numbered area on the map is presented
in rough detail, including a description of the overall geography
of the region, its major inhabitants and resources, and any
unique features you might find useful in adventuring. Obviously,
each area must be mapped in more detail if you plan to run your
campaign there. If you wish to add some three-dimensional detail
to your mapping, see page 114 for suggestions. Geomorphic
mapping is also described there and can be a great time-saver if
your PCs spend a lot of time adventuring in the regions of
Deepearth.

If you are employing one of the Hollow Earth theories, note that
the region of the hollow earth lies below the areas depicted on the
map of Deepearth. You will probably wish to create shafts or tunnels
leading down from the lowest level of Deepearth.

Connecting Passages of Deepearth

The map shows a number of connecting links between the
major inhabited regions of Deepearth. Some of these are shown
as waterways, while others are presented as tunnels. All connecting
passages are large enough to be passable to human-sized
characters. Other factors, such as vertical obstacles or water currents
are handled on an individual basis in the area description,
or can be generated randomly by the DM.

Water Passages

The waterways shown on the map are rivers flowing through
the vast dark reaches of Deepearth. With a quick look at the map,
it should be easy to determine which direction each river is flowing.
With the exception of waterfalls, the rivers proceed at a rapid
pace or slower, sometimes becoming almost stagnant in their
sluggishness.

All vertical drops, or waterfalls, are indicated on the map. Use
the map scale to determine how far a waterfall drops. All other
sections of underground waterways are navigable by boat,
assuming a skilled pilot and a little luck.

To determine the width of a section of waterway, roll ld6 and
multiply the result by 10, for a possible spread of 10-60 feet. The
width remains constant, with minor fluctuations, for one mile,
after which you must roll another d6. On a 2-5, the river remains
at approximately the same width. If the result is 1, the river
decreases in width by 10 feet (or 5 feet, if it is already only 10 feet
wide). If the result is a 6, the river expands its width by 10 feet,
even if this makes it wider than 60 feet.

The water in underground rivers is usually numbingly cold. To
check the temperature of a given area, roll 1 d6. On a 1-5, the river
is very cold. On a 6, some heat is reaching the water. To determine
how warm the water is, roll another d6. On a 1, the water is
cool, but slightly warmer than normal. On a 6, it is boiling hot. A
result ranging from 2-5 means a degree of warmth proportional to
the roll. Only water that is boiling hot is unsafe for unprotected
characters to swim or fall into.

Tunnels

The tunnels connecting the larger realms of Deepearth are all
of sufficient diameter to allow a human to pass, and often are
much wider than this. In most cases, these tunnels are natural
caverns, but about 1 out of every 10 miles (10% chance) has
been carved by intelligent creatures. In cases where excavation
has occurred, the tunnel is a uniform 10-foot diameter and height,
with no sudden obstacles such as cliffs or chasms.

There is a base 33% chance per mile that an obstacle lies in
the path of the PCs as they explore natural caverns. The obstacle
might be a cliff of 10d10 feet height, or a chasm 20d10 feet deep
and 4d10 feet wide. Other possible obstacles include the remnants
of a cave-in, or a large pool of water, quicksand, oil, or tar.

The obstacle never completely closes off the passage, however.
The caverns range from 3-60 feet (3d20) wide. Once a width
has been established, it remains constant for 100-2,000
(1d20 x 100) feet. After this distance, it stands a 113 chance of
changing. If a change is indicated, reroll the 3d20 to determine
the new width of the passage.

Various unintelligent monsters, including scavengers, occasionally
live in these passages, as do a wide variety of fungi,
molds, and lichens. However, intelligent creatures do not dwell
here. If an encounter with drow or any of the other intelligent
Underdark denizens is desired, it can certainly be designed, but
the encountered individuals will be passing through the tunnel,
not living there. Of course, renegade bands that have been banished
from their homelands might try to eke out an existence in
the tunnels.

Area Details

The map provided shows much too large an area to be fully
detailed in this volume. Instead, an overall framework is given
and the DM is free to fill in the necessary details. Each numbered
area is described in terms of its overall geography and origin, as
well as its most significant inhabitants. Any available resources
and any unique features are also described.

In terms of specific areas, however, you need to create some
maps of your own. General information indicates the overall
parameters of an area. For example, if a dungeon is described as
occupying a 300-foot-square area, this means that the dungeon
can be mapped in a 30 square by 30 square section of graph
paper, not that the dungeon is one huge room, 300 feet long on a
side. If you don’t have time to prepare a map, consider using the
Random Dungeon Generation system in the DMG, page 169.