Ancient Blue Dragon

Gargantuan dragon, Lawful Evil

Armor Class22 (natural armor)
Hit Points481 (26d20 + 208)
Speed40 ft., burrow 40 ft., fly 80 ft.
STRDEXCONINTWISCHA
29 (+9) 10 (+0) 27 (+8) 18 (+4) 17 (+3) 21 (+5)
Saving ThrowsCha +12, Con +15, Dex +7, Wis +10
SkillsPerception +17, Stealth +7
Damage Vulnerabilities—
Damage Resistances—
Damage Immunitieslightning
Condition Immunities—
Sensesblindsight 60 ft., darkvision 120 ft., passive Perception 27
LanguagesCommon, Draconic
Challenge23

Traits

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 three attacks: one with its bite and two with its claws.

Bite.

Melee Attack Roll: +16 to hit, reach 15 ft., one target. Hit: 20 (2d10 + 9) piercing damage plus 11 (2d10) lightning damage.

Claw.

Melee Attack Roll: +16 to hit, reach 10 ft., one target. Hit: 16 (2d6 + 9) slashing damage.

Tail.

Melee Attack Roll: +16 to hit, reach 20 ft., one target. Hit: 18 (2d8 + 9) 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 20 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.

Lightning Breath (Recharge 5-6).

The dragon exhales lightning in a 120-foot line that is 10 feet wide. Each creature in that line must make a DC 23 Dexterity saving throw, taking 88 (16d10) lightning damage on a failed save, or half as much damage on a successful one.

Legendary Actions

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 15 feet of the dragon must succeed on a DC 24 Dexterity saving throw or take 16 (2d6 + 9) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.