Vaurethiax, the Ember Beneath Mountains

gargantuan dragon (ancient), Neutral Evil · CR 24

by Emberquill Vance

Armor Class: 22

Hit Points: 546

Speed: 40 ft., climb 40 ft., fly 80 ft.

Saving Throws: dexterity, constitution, wisdom, charisma

Skills: History +11, Insight +10, Perception +10, Stealth +7

Damage Resistances: Bludgeoning (nonmagical), Piercing (nonmagical), Slashing (nonmagical)

Damage Immunities: Fire

Senses: blindsight 60 ft., darkvision 120 ft., passive Perception 20

Languages: Common, Draconic, Ignan, Terran

Challenge: 24 (62,000 XP)

STR 30 (+10)

DEX 10 (+0)

CON 29 (+9)

INT 18 (+4)

WIS 17 (+3)

CHA 25 (+7)

Traits

Legendary Resistance (3/Day). If Vaurethiax fails a saving throw, it can choose to succeed instead.
Molten Core. Vaurethiax runs hot enough to soften stone. A creature that starts its turn within 10 feet of it takes 10 (3d6) fire damage, and any nonmagical metal object that remains within 10 feet for 1 minute is ruined by warping.
Siege Monster. Vaurethiax deals double damage to objects and structures. Mountain roads, bridges, and mine props do not survive its passage through them.

Multiattack. The dragon makes one Bite attack and two Claw attacks.
Bite. Melee Weapon Attack: +17 to hit, reach 15 ft., one target. Hit: 2d10 + 10 piercing damage. The target takes an extra 14 (4d6) fire damage from the furnace heat of the dragon's throat.
Claw. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 2d6 + 10 slashing damage. Talons the colour of cooling slag, each one longer than a tall man.
Tail. Melee Weapon Attack: +17 to hit, reach 20 ft., one target. Hit: 2d8 + 10 bludgeoning damage. The target must succeed on a DC 25 Strength saving throw or be pushed 15 feet away and knocked prone.
Fire Breath (Recharge 5-6). Hit: 18d6 fire damage. The target must succeed on a DC 24 Dexterity saving throw, taking half as much damage on a successful one. Vaurethiax exhales a torrent of white fire in a 90-foot cone. Nonmagical objects in the area that are not being worn or carried are reduced to slag.

Bank the Coals. Vaurethiax draws its inner fire inward, dimming to the colour of dark iron. Until the start of its next turn it has resistance to all damage, but its Molten Core trait does not function and it cannot use Fire Breath.

Ember Retort. Molten blood sprays from the wound. The triggering creature must make a DC 24 Dexterity saving throw, taking 21 (6d6) fire damage on a failed save, or half as much on a successful one.

Detect. Vaurethiax makes a Wisdom (Perception) check.
Tail Sweep.
Wing Attack. Vaurethiax beats its wings. Each creature within 20 feet must succeed on a DC 25 Dexterity saving throw or take 17 (2d6 + 10) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.

Magma Vent. A fissure opens beneath a point the dragon can see within 120 feet. Each creature within 20 feet of that point must succeed on a DC 24 Dexterity saving throw or take 21 (6d6) fire damage. The fissure remains as difficult terrain.
Shifting Deeps. The mountain settles. Loose stone falls in a 30-foot-radius area the dragon chooses; each creature there must succeed on a DC 24 Dexterity saving throw or take 10 (3d6) bludgeoning damage and be restrained until it escapes with a DC 20 Strength (Athletics) check.

The Warm Rivers. Water within 6 miles of the lair runs blood-warm and never freezes. Crops fail from root rot, but the valleys stay green in deep winter, which is why people keep settling there against all advice.
Ash Weather. Fine grey ash falls within 6 miles of the lair. Visibility in the open is halved, and creatures that spend more than 24 hours in the area without protection gain one level of exhaustion that a long rest does not remove until they leave.