Adult Deep Dragon

Huge Dragon, Neutral Evil

AC: 17

Initiative: +10 (20)

HP: 161 (17d12 + 51)

Speed: 40 ft., burrow 30 ft., fly 80 ft., swim 40 ft.

STR
20 (+5)
DEX
14 (+2)
CON
17 (+3)
INT
16 (+3)
WIS
16 (+3)
CHA
18 (+4)

Saving Throws: Dex +6, Wis +7

Skills: Perception +11, Stealth +10

Resistances: poison; psychic

Condition Immunities: charmed; frightened; poisoned

Senses: Blindsight 60 ft., Darkvision 150 ft., Passive Perception 21

Languages: Common, Draconic, Undercommon

CR: 11 (XP 7,200, or 8,400 in lair; PB +4)

Habitat: Underdark

Treasure: Arcana

Legendary Resistance (3/Day, or 4/Day in Lair).

If the dragon fails a saving throw, it can choose to succeed instead.

Actions

Multiattack.

The dragon makes three Rend attacks.

Rend.

Melee Attack Roll: +9, reach 10 ft. Hit: 14 (2d8 + 5) Slashing damage plus 5 (1d10) Poison damage.

Nightmare Breath (Recharge 5-6).

Wisdom Saving Throw: DC 15, each creature in a 30-foot Cone. Failure: 38 (7d10) Psychic damage, and the target has the Frightened condition until the end of the dragon's next turn. Success: Half damage only.

Bonus Actions

Shape-Shift.

The dragon shape-shifts into a Small or Medium Humanoid or a Small or Medium Beast, or it returns to its true form. Its game statistics, other than its size, are the same in each form. Any equipment it is wearing or carrying isn't transformed.

Legendary Actions

Legendary Action Uses: 3 (4 in Lair). Immediately after another creature's turn, this creature can expend a use to take one of the following actions; it regains all expended uses at the start of each of its turns.

Pounce.

The dragon moves up to half its Speed, and it makes one Rend attack.

Spore Salvo.

Constitution Saving Throw: DC 15, one creature within 30 feet of the dragon that it can see. Failure: 13 (3d8) Poison damage, and the target has the Poisoned condition. It repeats the save at the end of each of its turns, ending the effect on itself on a success. After 1 minute, it succeeds automatically. Failure or Success: The dragon can't take this action again until the start of its next turn.

Regional Effects

The region containing an adult or ancient deep dragon's lair is changed by its presence, creating the following effects:

  • Preservation of Knowledge.

    Books and other written forms of communication with 1 mile of the lair become magically protected and can't be damaged by nonmagical means.

  • Restless Sleep.

    When a creature finishes a Long Rest within 1 mile of the lair, the creature makes a DC 10 Constitution saving throw. On a failed save, the creature doesn't reduce its Exhaustion level as a result of finishing that Long Rest. Creatures with Immunity to the Poisoned condition are immune to this effect.

  • Verdant Growth.

    Vegetation and fungi within 1 mile of the dragon's lair grow faster and cover a greater area than normal. Foraging in this area yields twice the usual amount of food. The dragon is immediately aware of the presence of any creature that eats this enhanced vegetation.

If the dragon dies or moves its lair elsewhere, these effects end immediately.

Find this creature in the encounter builder

Adult Deep Dragon

Source: The Lost Library of Lethchauntos, p. 258 - Licenses and attribution