Geography: This yawning chasm stretches over ten miles in
length, and is fully a mile wide. The ceiling of the cavern arches
naturally, and the AREA has withstood many a tumultuous earthquake
and other natural disaster. The ceiling is about 200 feet
high at the point where the tunnel from Area 6 enters. The canyon
walls gradually grow closer together as they descend. They meet
in a boulder-and-rubble-filled gorge over a mile below.
The canyon was originally excavated by water erosion. In fact,
a great river once cut a path through it. The same shift in water
table that dried up the duergar wells caused the river to cease
flowing. The canyon is now similar to a dead cave, except that
few cave formations have developed. It is not as dusty here as in
some other regions, perhaps because of the faint breezes
brought by circulating air.
The walls of the canyon are cracked and riddled with ledges,
chimneys, and other irregularities. The rock is old, but generally
stable-it is not likely to break off when climbed. No bridges
cross it at this height.
Across the canyon from the access tunnel, the cavern continues
to wind into the earth. About 3,000 feet below this level,
another series of caverns enters into the canyon on one side and
continues out the other. These caverns are about two miles south
of the tunnels on the upper level, so characters scaling straight
down the walls do not discover them.
The walls of the canyon are pockmarked regularly with limestone
caves, some of them as deep as 300 feet. These cave
mouths occur at intervals of about 500 feet above, below, and to
the sides of each other. In some cases they are closer together,
and in others more widely separated.

At the ceiling of the cavern, several narrow vertical shafts lead
upward to join a major tunnel that eventually connects with the
sewer system of the large city on the surface. These tunnels
range from 1-3 feet in diameter, and often climb straight up, so
they are of little use to any creatures except bats.

Denizens: Bats inhabit the canyon in great numbers. Most of
these are of the harmless normal varieties, but several hundred
mobats also live in the canyon. The latter subsist off of the former
to a great extent, but the mobats also aggressively attack any
large warm-blooded canyon intruders. Fortunately for said
intruders, the mobats do not attack all together, but in groups of
2d6 at a time.
Several of the small caves branching off the canyon are the
lairs of cave fishers. These voracious carnivores attempt to strike
any flying or climbing creatures that come within their reach. The
bottom of the canyon is regularly scoured by a pair of giant slugs.
Many of the smaller side caves are inhabited by giant centipedes,
and carrion crawlers regularly move up and down the walls.
The only intelligent denizens are a small group of cloakers living
in one of the highest and most remote of the side caves. The
cloakers are 50% likely to be attracted if the mobats attack an
intruder. The cloakers fly to the combat scene and wait for the
bats to either be driven off or claim their victim. After the fight, the
cloakers close in and polish off the wounded intruders or seize a
few of the bats.
The cloaker community numbers about two dozen individuals.
They do not attack as a group, however. If an encounter occurs,
balance the number of cloakers used with the levels of your
PCs.

Resources: This canyon has a plentiful supply of fresh air
because of all the access tunnels leading to it. Water is much less
abundant, however; it is confined to a number of stagnant pools
among the rocks at the bottom of the canyon. While some of
these pools are very large and deep, none of them receives any
fresh flowing water. Characters who drink the water have a 50%
chance of contracting a disease, as in the cause disease spell
effect. <WSG: Effects of Drinking Tainted Water>
Food supplies are limited to the creatures living here and a few
lichens and fungi growing in narrow niches upon the canyon
walls.