Legendary Resistance (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.
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) fire 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.
Fire Breath (Recharge 5–6). The dragon shoots a line of fire in a 100--foot line that is 15 feet wide. Each creature in that line must make a DC 23 Dexterity saving throw, taking 88 (16d10) fire damage on a failed save, or half as much damage on a successful one.
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.
Detect. The dragon makes a Wisdom (Perception) check.
Tail Attack. The dragon makes a tail attack.
Throw rock and stone (Costs 2 Actions). The dragon claws loose a huge rock from the cavern walls and throws it at a point on the ground within 60 ft, hitting a 4ft square. Each creature within the square must attempt a DC 24 Dexterity saving throw. Taking 26 (2d10 + 9) bludgeoning damage and be knocked prone on a failed save, or half the damage and not be knocked prone on a success.
Lair and Lair Actions
Tunneling dragons make their lairs deep within the mountains. Using their burrowing ability to carve out caverns and tunnels beneath the mountains, preferring warm caverns close to lava rivers.
Rivers of molten rock often surrounds most entrances to a tunneling dragons lair, making it nigh impossible to navigate to. They can dig through the rock itself and climb vertical rockwalls as if running forwards.
A tunneling dragon may collapse the caverns that make up its lair if that lair is invaded. The dragon then burrows out, leaving its attackers to be crushed and suffocated. When it returns later, it collects its possessions — along with the wealth of the dead intruders.
Lair Actions
On initiative count 20 (losing initiative ties), the dragon takes a lair action to cause one of the following effects; the dragon can’t use the same effect two rounds in a row:
- Part of the ceiling collapses above one creature that the dragon can see within 120 feet of it. The creature must succeed on a DC 15 Dexterity saving throw or take 10 (3d6) bludgeoning damage and be knocked prone and buried. The buried target is restrained and unable to breathe or stand up. A creature can take an action to make a DC 10 Strength check, ending the buried state on a success.
- An eruption of hot steam sprays out in a 20-foot-radius sphere centered on a point the dragon can see within 120 feet of it. The spray spreads around corners. Each creature in the area must succeed on a DC 15 Constitution saving throw or be blinded 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.
- An eruption of lava centered on a point on the wall, ceiling or floor within 120ft of the dragon. The eruption sprays out in a 20 ft square. Each creature in that square must succeed on a DC 15 Dexterity saving throw or take 10 (3d6) fire damage.
Regional Effects
The region containing a legendary tunneling dragon’s lair is warped by the dragon’s magic, which creates one or more of the following effects:
- Increased volcanic activity within 6 miles.
- Lesser fire and earth elementals scour the land within 6 miles of the lair. Drawn to the high volcanic activity and shifting of earth.
- Hidden sinkholes form in and around the dragon’s lair. A sinkhole can be spotted from a safe distance with a successful DC 20 Wisdom (Perception) check. Otherwise, the first creature to step on the thin crust covering the sinkhole must succeed on a DC 15 Dexterity saving throw or fall 1d6 × 10 feet into the sinkhole.
If the dragon dies, the elementals disappear and the voncanic activity abate within 1d10 days. Any sinkholes remain where they are.
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