globs of edible gray slime. (The mind flayers use these
dishes to bring food to prisoners in area 10.)
Wall of Force. The rubble-strewn passage to area 8a is
blocked by an invisible wall of force that is generated
from area 16c.
The mind flayers gained control of two s caladar (see
appendix A) and implanted duergar brains in them,
bestowing on each construct an Intelligence of 11 and
the ability to understand (but not speak) Dwarvish and
Undercommon. Each duergar brain is contained in a
glass sphere embedded in the construct's head. These
scaladar obey the commands of illithids and attack
any creatures that aren't mind flayers or their thralls.
Trobriand's rings no longer have any effect on these
constructs.16B. SOUTH GUARD POST
This misshapen, 20-foot-high room sits at the top of
a sloped tunnel that descends for hundreds of feet to
level 18. Guarding the otherwise empty room are eight
duergar. If they see light approaching, the duergar turn
invisible and enlarge themselves, then ambush anyone
that enters the chamber. These duergar have had their
minds broken by the mind flayers and fight to the death.16c. PSIONIC FORCE GENERATOR
Pedestal. In the middle of the room, two m ind flayers
grip the top of a 4-foot-tall, three-sided crystal pedes-
tal with a fist-sized diamond floating 1 foot above it.
Anvils. Piled against the walls are scores of rusty iron
anvils forged and abandoned long ago by the Me-
lairkyn dwarves. (Each one weighs 500 pounds.)
The crystal pedestal with the diamond levitating
above it is a psionic force generator, a magic device that
allows the mind flayers to create and sustain the walls of
force that enclose area 8. The mind flayers provide the
mental energy that powers the generator. If these mind
flayers are attacked, one maintains contact with the
crystal pedestal while the other defends it.
The diamond no longer floats if removed from its
place above the pedestal. A creature within reach of the
diamond can use an action to take it. Without the dia-
mond, the generator shuts down and the walls of force
in area 8 disappear. The device can't function without
the diamond (or another of the same or greater value).
The walls of force also disappear if the mind flayers
are pulled away from the pedestal- though the walls
reappear if contact is reestablished, as long as the dia-
mond is still floating in place. If the walls disappear, the
neothelid in area 8 escapes in search of prey, killing and
consuming any creatures it finds.
The crystal pedestal is embedded in the floor and
can't be knocked over, but it can be destroyed, rendering
the generator irreparable. The pedestal is a Small object
with AC 13, 20 hit points, and immunity to poison and
psychic damage.
Treasure. The diamond is worth 5, 000 gp.
LEVEL 17 I SEADEEPS
- CRU MBLING BRIDGE
Spanning the river at this point is a crumbling stone
bridge that can support 200 pounds at a time. Any more
weight causes it to collapse. A creature on the bridge
when it collapses can leap to one side or the other with
a successful DC 15 Dexterity saving throw. On a failed
save, the creature falls in the river and might get swept
away (see "Underground River," page 227). - GR AY MOLD
The walls of this room are streaked with a slimy gray
mold, some of which has been scraped off. Under the
mold are bas-relief sculptures of dwarves chopping
down large mushrooms.
The mold growing here is edible and nutritious, but
not tasty. The mind flayers feed it to their prisoners. A
small cup of the mold is nutritionally equivalent to a
day's worth of rations.
1 9. UNGUARDED AREA
Neither the mind flayers nor their thralls come here.19A. RIVER'S ROAR
Creatures in this 10 -foot-high, partially collapsed cham-
ber have disadvantage on Wisdom (Perception) checks
that rely on hearing due to the loud roar of the under-
ground river nearby.19B. SAFE SHORELINE CAVE
The 10-foot-high, rough-hewn chamber is strewn with
rubble. The shore is rocky and covered with loose dirt.20. RIVER BRANCHES
The river (see "Underground River," page 227) reaches
a depth of 20 feet at this point, where it splits off in three
directions. A creature swept along by the river's strong
current is pulled in a random direction determined by
rolling a d6. On a 1, the creature is swept into area 12a.
On a 2, the creature is swept into area 12b. On any other
result, the creature is swept into area 12c.Aftermath
If freed from its confinement, the neothelid wanders
Seadeeps and consumes any other creature that crosses
its path. Characters might try luring it to another level of
Undermountain, where it can wreak even more havoc.
If the neothelid becomes too great a nuisance, Halaster
takes strides to either destroy or contain it.
Killing Extremiton completes a quest (see "Uncover
the Telepathic Spy," page 10). Deprived of their
leader, the surviving illithids disappear into other cor-
ners of Undermountain or return to the Underdark.
With the illithids gone, the githyanki move to secure
the level with reinforcements from level 16-assuming
there are any githyanki left. If the githyanki are wiped
out and Extremiton is allowed to live, it eventually turns
itself into an elder brain, which attracts more illithids to
the colony. In addition, the illithids continue to capture
people from Waterdeep for their Alterdeep simulation,
which grows more intricate and nuanced every day.