Ancient Water Dragon

Gargantuan dragon, neutral good

Armor Class 22 (natural armor)

22 (natural armor) Hit Points 388 (21d20 + 168)

388 (21d20 + 168) Speed 40 ft., burrow 20 ft., swim 80 ft.

STR DEX CON INT WIS CHA 26 (+8) 14 (+2) 26 (+8) 20 (+5) 18 (+4) 19 (+4)

Saving Throws Dex +9, Con +15, Wis +11, Cha +11

Dex +9, Con +15, Wis +11, Cha +11 Skills Perception +18, Stealth +9

Perception +18, Stealth +9 Damage Resistances fire

fire Damage Immunities acid

acid Senses blindsight 60 ft., darkvision 120 ft., passive Perception 28

blindsight 60 ft., darkvision 120 ft., passive Perception 28 Languages Aquan, Common, Draconic

Aquan, Common, Draconic Challenge 21 (33,000 XP)

Amphibious. The dragon can breathe air and water.

Legendary Resistance (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.

Actions

Multiattack. The dragon can use its Frightful Presence. It then makes two attacks: one with its bite and one with its tail.

Bite. Melee Weapon Attack: +15 to hit, reach 15 ft., one target. Hit: 19 (2d10 + 8) piercing damage.

Tail. Melee Weapon Attack: +15 to hit, reach 20 ft., one target. Hit: 26 (4d8 + 8) bludgeoning damage.

Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 19 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.

Water Breath (Recharge 5-6). The dragon exhales a powerful stream of water in a 90-foot line that is 10 feet wide. Each creature in that line must make a DC 23 Dexterity saving throw, taking 77 (14d10) bludgeoning 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.