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QUALITH DOOR LOCKS
Mounted on both sides of every door in the mind flayer
colony (areas 9 through 20) is a burnished plate of dark,
alien metal embossed with a braille-like form of tactile
writing known as Qualith. Mind flayers use their tentacles
to read Qualith, which is composed in four-line stanzas
indecipherable to other creatures. A creature that touches
a Qualith inscription, however, can receive fragmentary
insight into the multilayered thoughts contained in it. A
non-illithid that wants to understand a Qualith inscription
in Seadeeps can make a DC^18 Intelligence check to inter-
pret the inscription. A failed attempt results in a crushing
headache and requires the creature to succeed on a DC
11 Wisdom saving throw or develop a random form of
short-term madness (see "Madness" in chapter 8 of the
Dungeon Master's Guide). A comprehend languages spell
provides understanding of the inscription roughly equiva-
lent to what a mind flayer would get from it.
Each door plate is imbued with psionic energy that func-
tions like an arcane lock spell. The Qualith inscription on
the plate describes the genuflections a mind flayer must
make with its tentacles to open the door. Other creatures
with at least four tentacles (such as flumphs) can imitate
these motions to bypass the lock, provided they can inter-
pret the inscription. A creature must be within 5 feet of the
door to open it in this way. Creatures without the requisite
tentacles and knowledge must deal with the lock by more
conventional means, such as a knock spell. If magic is un-
available, a locked door can be forced open with a success-
ful DC 30 Strength (Athletics) check.
Clever adventurers might discover that a decapitated
mind flayer head, animated through an animate dead spell,
can be used to access the locks.
In the heart of Seadeeps, the ulitharid has built an
enormous dynamo that channels the energy of an under-
ground river to power a series of interconnected metal
capsules called psipods. The illithids under Extremi-
ton's command have kidnapped humanoids from Water-
deep and Undermountain and put them to sleep in these
capsules, which link their dreaming minds to the ulitha-
rid's dizzying intellect. These captives believe they're in
Waterdeep, but the city they see and experience around
them is a fabrication created wholly by the ulitharid.
Within this alternate reality Waterdeep, or "Alterdeep,"
Extremiton appears as any character it wants. Its favor-
ite role to play is that of Durnan, the gruff, tight-lipped
proprietor of the Yawning Portal.
Extremiton can make any environmental changes to
Alterdeep and observe how its captive audience reacts.
Meanwhile, it continues to use its telepathy to reach out
to the Waterdavians in the city above, gathering more
information to better realize its version of the city.
GITHYANKI
After tracking the splinter colony of mind flayers to Un-
dermountain, githyanki forces from level 16 have begun
their systematic eradication of the illithid presence.
The githyanki forces on this level await reinforce-
ments from level 16. Yaveklar, the knight in command,
intends to personally cut off the ulitharid's head and
present it to her superiors. Her second in command,
Lashiir, wants to see Yaveklar stripped of her command
for incompetence.
LEVEL 17 I SEADEEl'S
Exploring This Level
All location descriptions for this level are keyed
to map 17.
The caverns surrounding the mind flayer colony are
dark and da mp. The space occupied by the colony is
smoothly carved from solid stone. Throughout this
level, adventurers hear the constant thunder of the un-
derground river, which is especially loud in area^12 and
slightly Jess so in areas 16 through 20.
- TuNNEL PLEXUS
The natural tunnel that descends from level 16 levels
out before splitting into several passages that connect
to areas 2, 5, and 6. These passageways have uneven
floors and ceilings, the distance between which varies
from 10 to 15 feet. Characters who navigate these tun-
nels occasionally come across the bodies of flumphs
slain by the githyanki.
2. DRIPPING CAVE
Water drips from stalactites that cling to the roof of this
damp, 30-foot-high cave.
3. HALASTER'S MAW
Most of this 30-foot-high cavern is taken up by a gaping
pit roughly 50 feet long, 30 feet wide, and 30 feet deep.
Its sides slope inward so that the floor of the pit is 30
feet long by 10 feet wide. A statue of a humanoid figure
lies shattered at the bottom of the pit.
The broken statue is all that remains of Aasathra
Raghthroknaar, a female dragonborn adventurer who
was turned to stone and placed here by Halaster to lure
other adventurers to their doom (see "Pit Trap" below).
PITThAP
A detect magic spell reveals an aura of transmutation
magic around the pit. Each time part of the statue is dis-
turbed, the pit magically snaps shut like a giant mouth
and then slowly opens again. Creatures in the pit when
it closes are crushed between its rocky walls and must
make a DC^17 Dexterity saving throw, taking^88 (16d10)
bludgeoning damage on a failed save, or half as much
damage on a successful one. Creatures that are gas-
eous, amorphous (such as an ooze), or protected by an
impenetrable magical barrier (such as that created by an
Otiluke's resilient sphere spell) take no damage.
4. FLUMPH CLOISTER
Flumphs. Stalactites cling to the roof of this 20-foot-
high cavern. Lurking among them are nine ftumpbs.
The flumphs are passive creatures that fight only in
self-defense.
Secret Door. A secret door in the south wall is carved to
resemble natural stone.
The flumphs telepathically share the following infor-
mation with friendly visitors:
- Mind flayers have established a splinter colony on this
level (areas 9 through 20). An ulitharid called Extremi-
ton leads the colony. Once the colony is secure and its