Ancient Blue Dragon

Gargantuan dragon, lawful evil
Armor Class
22
Hit Points
26d20 + 208 (481)
Speed
walk
40 ft.
fly
80 ft.
burrow
40 ft.

STR
29 (+9)
DEX
10 (+0)
CON
27 (+8)
INT
18 (+4)
WIS
17 (+3)
CHA
21 (+5)

Saving Throws Cha +12, Con +15, Dex +7, Wis +10
Senses blindsight 60 ft., darkvision 120 ft., passive Perception 27
Languages Common, Draconic
Challenge 23 (50,000XP)

Damage Immunities
lightning

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

Claw

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

Tail

Melee Weapon Attack: +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 ft. 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.