D&D 5E - The Rise of Tiamat

A steep slope descends from the cave behind the
waterfall to the entrance to area 2, its surface slick
from billowing mist. A character must succeed on a DC
12 Dexterity (Acrobatics) check or a D C 12 Strength
(Athletics) check to climb or crawl down the slope.
Failure indicates that the character tumbles 40 feet
down the slope, taking 9 (2d8) bludgeoning damage.
Characters using a rope to descend the slope can
do so safely.
D r a g o n A t t a c k
If the characters wear the garlands given to them by the
druid, Chuth has no idea of their approach, allowing
them to safely pass through this area and into the caves.
If the adventurers did not receive the garlands, or if
they took them off for any reason while within a quarter
mile of Chuth’s lair, the dragon’s many animal spies
alert him to the party’s approach. He waits at the mouth
of the cave, clinging to the wall near the entrance.
A character who succeeds on a DC 20 Wisdom
(Perception) check notices movement inside the cave but
can’t tell what it is (or how large a creature it might be).
Chuth uses his blindsight to detect when the
characters are approaching the entrance to the cave.
He then dives through the waterfall, soaring above the
characters as he uses his Poison Breath, attacking with
surprise if no one in the party noticed him. Characters
not wearing the garlands are also exposed to the
dragon’s Frightful Presence. Characters who fail their
saving throws against Frightful Presence likely flee
back into the woods, where spiders might be waiting.
On the dragon’s next turn, it retreats back to area 2 to
await the heroes’ next move.
2. Is l a n d C h a m b e r
This large chamber has a 40-foot-high ceiling set with
massive stalactites, with smaller stalagmites set across
the ground. A pool with a small island in the southeast
corner of the cavern is fed by streams of water dripping
down through the rock. The southwest face of the
cavern is a 25-foot-high bluff, part of which is area 4.
No O ne Home
When the characters approach the stronghold, there
might be a chance that Chuth has left the caves to hunt, or
that he and Neronvain are out scouting future raids. You
can determine this randomly as you see fit, or allow the
characters to hole up within sight o f the stronghold and
simply wait for the dragon and the wyrmspeaker to leave.
Removing Chuth and Neronvain from the stronghold for an
initial foray allows the characters to explore and eliminate the
guards without the pressure o f an imminent dragon attack.
This dungeon is a tough adventure even for higher-level
characters, especially with the legendary actions Chuth can
use in his lair. Attacking head-on if the dragon is aware o f the
adventurers' approach is likely a suicide mission.