Huge dragon (plant), lawful neutral

Armor Class: 19 (natural armor)

Hit Points: 207 (18d12 + 90)

Speed: 40 ft , fly: 80 ft , swim: 40 ft

STR

20 +5

DEX

15 +2

CON

20 +5

INT

19 +4

WIS

18 +4

CHA

15 +2

Saving Throws: Dex +7, Con +10, Wis +7, Cha +8

Skills: Deception +8, Insight +7, Perception +12, Persuasion +8, Stealth +7

Damage Vulnerabilities: fire

Damage Immunities: poison

Condition Immunities: blinded, deafened, poisoned

Senses: blindsight 120 ft., passive Perception 22

Languages: Common, Draconic

Challenge Rating: 15

Proficiency Bonus: +5

Actions

Multiattack. The dragon makes three attacks: one with its bite and two with its claws. Bite. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 16 (2d10 + 5) piercing damage.   Claw. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 5) slashing damage.   Tail. Melee Weapon Attack: +10 to hit, reach 15 ft., one target. Hit: 14 (2d8 + 5) bludgeoning damage.   Plant Roots. The dragon roots itself into the ground, reducing its movement to 0 feet but regains 11 (2d10) hit points at the start of each of its turns. The dragon can retract its roots as a bonus action.   Poison Breath (Recharge 5-6). The dragon exhales poisonous gas in a 60-foot cone. Each creature in that area must make a DC 18 Constitution saving throw, taking 56 (16d6) poison damage on a failed save, or half as much damage on a successful one.

Legendary Actions

The dragon can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The dragon regains spent legendary actions at the start of its turn. Detect. The dragon makes a Wisdom (Perception) check. Tail Attack. The dragon makes a tail attack. Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 10 feet of the dragon must succeed on a DC 19 Dexterity saving throw or take 13 (2d6 + 6) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.