Geography: This large region of natural caverns was formed
by water erosion, but its character has since been altered by
major subterranean upheavals. Fiery volcanic action in nearby
sections of Deepearth created sharp fissures throughout the
rock, and some of these cracks in the world tapped into the
caverns .

The meandering river from the Lower Lake reaches a cavern
about five miles south of the main chambers of this area. This
connecting cavern is the source of a rapid stream of relatively hot
water that joins the river. The river, at this point, begins to pick up
speed as the the riverbed starts to descend more steeply. A wide
shoreline coated with a beach of fine sand provides an easy landing
for boat traffic.

The tunnel containing the hot stream was originally part of the
area’s natural caverns, but it has been artificially expanded to
handle an increased flow of water. Its course has been straightened
and its rate of descent increased, so that the hot water
races down a veritable chute into the river.

The main area of caverns contains six large caves that are connected
by several narrow passages. The air is steamy and hot,
and water coats all rock surfaces. Large pools of water fill the low
spots in many of the caverns. Their temperatures range from boiling
hot to relatively cool. Mildew on most of the rock surfaces
makes everything extremely slippery.

A tunnel leading to the north connects with Area 21. This natural
cavern is subject to blasts of superheated air about once an
hour (2% chance per round, cumulative; Le., 2% the first round
after a blast, 4% the next round, 6% after that, etc.). Characters
in the tunnel at the time sustain 4d6 points of damage, although
they can save vs. breath weapon for half damage. Of course, normal
fire resistance benefits might reduce this damage.

The tunnel leading to the east is the source of the stream that
flows out of the area. As the water flows through this area, however,
it becomes much hotter. The entire cavern feels very hot,
and the water inflicts 4d6 points of damage per round, with saves
as above. If characters are only partly immersed in the water,
reduce the damage accordingly.

Denizens: As might be expected, this is a favorite haven for
creatures who love fire and heat. In Area 21, the connection to the
Elemental Plane of Fire has enabled creatures from that infernal
place to proliferate.

Efreet, fire elementals, salamanders, and fire bats are all creatures
from the Plane of Fire that can be encountered here. While
they may be hostile and aggressive, they are far enough from
their escape routes that they will not hesitate to flee an encounter
that is going badly.

Other creatures, including hell hounds, giant rats, green slime,
carrion crawlers, and even megalo centipedes, have made these
caverns their lairs, and fight with normal tenacity.
The most formidable inhabitants of the area are the fire giants,
who hold sway over all the other denizens. Occasionally accompanied
by packs of hell hounds, fire giants restlessly roam among
the large caverns, bullying the lesser creatures and slaying any
who resist. Although they claim the largest cavern as their lair, the
fire giants are basically nomadic and may be encountered in any
part of this cave network. When assembled, the clan of fire giants
numbers over 50 individuals.

Resources: The air in these caverns is muggy && oppressive,
and characters unused to the environment become fatigued in half the usual time.
Water is plentiful, and food in the form of
fungi is also abundant. No mineral wealth has been located here.

Unique Features: Several of the caverns in the area contain
geysers capable of spouting of scalding water and steam every
bit as lethal as a red dragon’s breath. A pool of water here is 20%
likely to be susceptible to geyser activity. In addition, a number of
narrow cracks and niches in the rock can issue such deadly
blasts. Characters caught in the force of one of these geothermal
eruptions sustain 6d6 points of damage, with saving throws vs.
breath weapon allowed to reduce damage to 1/2. Fire resistant
benefits can further reduce the damage.