CR 20
Gargantuan Dragon
Armor Class 21 (natural armor)
Hit Points 355
Speed 40 ft., burrow 40 ft., fly 80 ft.
Perception 27 Stealth 16
ResistantIf the dragon fails a save, it can choose to succeed instead.
Immune lightning
Sensesdarkvision 120 ft., keensense 60 ft.
Languages Common, Draconic
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| +9 | +6 | +14 | +4 | +9 | +11 |
Charged Hide. When the blue dragon hasn’t exhaled its Lightning Breath, the electric charge builds up across its body. While the dragon’s Lightning Breath is available, it emits wild sparks of electricity, and each creature that starts its turn within 30 feet of the dragon must succeed on a DC 22 CON save or be incapacitated until the start of its next turn.
Legendary Resistance (3/Day). If the dragon fails a save, it can choose to succeed instead.
Actions
Multiattack. The dragon uses its Frightful Presence. It then makes one Bite attack and two Claw attacks.
Bite. Melee Weapon Attack: +15 to hit, reach 15 ft., one target. Hit: 20 (2d10 + 9) piercing damage plus 11 (2d10) lightning damage.
Claw. Melee Weapon Attack: +15 to hit, reach 10 ft., one target. Hit: 16 (2d6 + 9) slashing damage.
Tail. Melee Weapon Attack: +15 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 19 WIS save or be frightened for 1 minute. A creature can repeat the save at the end of each of its turns, ending the effect on itself on a success. If a creature’s save 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 22 DEX save, taking 99 (18d10) lightning 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 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 automatically detects every creature and trap within 30 feet of it, pinpointing the current location of each.
Tail Attack. The dragon makes a Tail attack.
Elemental Roar (Costs 2 Actions). The dragon roars at up to two creatures of its choice within 120 feet of it. Each target must succeed on a DC 19 CHA save or be vulnerable to lightning damage until the end of its next turn. A target resistant to lightning damage isn’t resistant to it for the duration. A target immune to lightning damage is still immune to it, even if the target fails the save.
Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 15 feet of the dragon must succeed on a DC 23 DEX save or take 16 (2d6 + 9) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed without provoking opportunity attacks.