D&D 5E - The Rise of Tiamat

the yuan-ti attacked and hauled him off. A stone sluice
runs from the southern wall to empty into the pool. If
the characters can fill the basin in area 5 and release
the sluice quickly enough, the water pours into the pool
before it has a chance to evaporate. Alternatively, the
pool can be activated with a flask of holy water, which is
not subject to the mummy lord’s lair effects.
When any water hits the pool, it spreads out and flares
with a black light. Any character who received Ilda’s
warning (or who remembers the statues in area 3) w ill
hopefully declare that he or she looks away from the
pool. Otherwise, a character must make a DC 20 saving
throw against a suggestion spell. On a failed save, the
character gazes into the divination pool unless another
character immediately pulls the curious victim away
from the pool (and avoids gazing into it as he or she
does so). If not pulled away, a gazing character is driven
temporarily insane for 1 minute (see area 3). A character
pulled away from the pool does not suffer insanity but is
stunned for 1 minute.
U s i n g t h e P o o l
The divination pool has always required that a user
make a personal sacrifice to gain its secrets. However,
the pool’s magic has grown considerably hungrier over
the long years of its isolation. In response to the cruelty
of the yuan-ti, using the pool requires the sacrifice of all
or a significant part of a sentient creature.
doom.” Diderius opens the way only for those who are
particularly decorous in this exchnage.
If the adventurers try to open the sarcophagus,
Diderius warns them. If they persist, he attacks. The
mummies behind the frescoes also smash free and
attack. None of the monsters pursue those who flee this
room, which soon returns to its original state.
Diderius can use mummy lord legendary actions,
but he is unusual because he casts wizard spells. He
uses his 18 Intelligence as his spellcasting ability (his
Wisdom remains 18) and has the following wizard
spells prepared:
Cantrips (at will): minor illusion, ray o f frost
1st level (4 slots): charm person, detect magic,
shield, thunderwave
2nd level (3 slots): cloud o f daggers, hold person, see invisibility
3rd level (3 slots): animate dead, dispel magic
4th level (3 slots)'.fire shield, greater invisibility
5th level (2 slots): cloudkill, wall o f stone
A canopic jar in the sarcophagus contains Diderius’s
withered heart.
Secret Door. In the northern wall is a secret door
(Intelligence [Investigation] DC 20 to find). Knocking
on the stone wall reveals a hollow echo beyond, but the
mechanism for opening the door is on the other side. A
knock or stone shape spell can open it, or the door can
be forced with a successful D C 20 Strength check.
13. C r y p t o f D id e r i u s
Diderius’s final resting place is a 20-foot-high chamber
lit by braziers imbued with continual flame. A massive
stone sarcophagus sits atop a stepped stone dais at
center. The walls are decorated with life-sized frescoes
showing the lost gods of Netheril and Anauria. If the
party benefits from the boon granted in area 1, all the
characters sense it would be disrespectful to disturb
anything here—everything should remain as it is.
Frescoes. Characters who examine the frescoes can
attempt a DC 15 Intelligence (Investigation) check to
discover thin plaster on four of them. If any such fresco
is broken open, a mummy hidden behind it attacks.
The other three hidden mummies, all once Diderius’s
advisers, smash free to attack thereafter.
Sarcophagus. Diderius, the mummy lord, rests
within the sarcophagus. When the characters approach
within a few paces of it, a deep, clear voice issues from
the coffin, saying, “You approach Diderius in repose. I
know what you seek.”
If the adventurers spoke well to the staues in area
1, the voice says, “Yuan-ti have taken the one called
Varram beyond their portal in the northern wall. Be
prepared, for I shall open the way to peril." Unless
the characters ask Diderius to wait, a moment later,
with a chiming sound, the secret door opens to area
14. The party gains a surprise round to act against the
guards there.
Those who didn’t speak well in area 1 must ask
Diderius about Varram to gain information about his
whereabouts. Failure to do so respectfully causes
Diderius to say, “Leave me to my rest or face your