Basalt dragon lairs are usually natural caves carved out by millenia of erosion from air and water. They rarely modify these caves or their surroundings, making it all the more easy for them to hide their massive bodies in plain sight. The caves they prefer are rocky coastlines formed through ancient volcanic activity, the more closely resembling their own bodies the better. The most prized lairs are those with sea facing entrances that have been hollowed out from waves beating the cavern walls deeper into the cliffside. These entrances can be difficult even for the dragon to navigate through gracefully, all the better to deter other dragons of their type, their only true equals. These caves tend to be large single chamber openings with plenty of room for the dragon to move. Often there are pools of water scattered along the floor that fill and drain with the tides, these pools are where the basalt dragons hide and hoard their most prized treasure; gemstones. These seemingly inert locations rumble and groan when the dragon fights intruders. The standing water crashes against hard rock forms, it refracts brilliant colored light from gemstones under its surface, and is super heated into steam from the dragon’s breath attacks to create a cacophonous and treacherous battlefield.

On initiative count 20 (losing initiative ties), the Basalt 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:

- The dragon calls forth a hexagonal pillar of solid basalt roughly 5 feet in diameter and 20 feet high that bursts from the ground within 120 feet of it. If a creature is standing in the space where the pillar rises it must make a DC 15 Dexterity saving throw, being thrown 40 ft in the air on a failed save, or moving out of the way to an adjacent safe space on a successful one.

- The basalt pillars created by the dragon begin to hum at a low-pitch, amplifying their latent magnetism. Any creature wearing medium or heavy armor, or equivalent metal composition on them, within 10 feet of any of the dragon’s basalt pillars must succeed on a DC 15 Strength saving throw or become restrained for one round.

- The basalt pillars created by the dragon begin to hum at a high pitch, glowing faintly with a dull red color in their core. Manufactured objects made of metal such as metal weapons or medium or heavy suits of armor within 10 feet of any of the basalt pillars glow red hot. Any creature in physical contact with any of the objects takes 2d8 fire damage. If a creature is holding or wearing any of the objects and takes the damage from it, the creature must succeed on a DC 15 Constitution saving throw or drop the objects if it can. If it doesn’t drop an object, it has disadvantage on attack rolls and ability checks for one round.

Basalt dragons are hulks of living primordial stone, powered by draconic blood that burns with a volcanic heat. When still, their forms blend into their natural surroundings, looking like geometric rock formations with a vague appearance of a dragon. But when provoked, their draconic lineage is unmistakable. Four thick legs support its stout frame which is covered in growths and ridges that resemble slow-cooled basalt rock; long and hexagonal in profile. Their wings are small, bordering on vestigial. Basalt dragons don’t fly, so much as jump with their powerful legs assisted by their wings. They have brutish stubby faces with features that, when at rest, link together to form solid rock, but then open up to reveal their superheated internal structures.

Basalt Dragons spend most of their lives waiting. Their infamous hoards of gemstones lure interlopers of all kinds into their lairs. The dragons are so still and rock-like in appearance that they blend into the strata that surround them, easily mistaken for a huge stone formation. A difficult perception check should be needed to see the dragon, lower if one knows what they’re looking for. Basalt dragons ambush trespassers with their pillar ability, and continue creating them every chance they get, increasing the effectiveness of their other abilities and creating choke points for their line of lava breath. They rarely take flight within their lairs but do use their Wing Attack liberally to bound from target to target, making sure to keep more dangerous enemies at a distance.

Nature DC 20 - Basalt Dragons are ambush predators that are naturally camouflaged in their lairs.

Arcana DC 15 - Basalt Dragons are ancient rock-like beings that have powers over earth and terrain.

Insight DC 10 - Basalt Dragons are evil in nature and are rarely interested in discussion. If you’re face to face with one, it is probably already trying to kill you.

Basalt Dragon hoards consist almost entirely of gemstones. They hide these in the pools of tidal water that rest in their coastal lairs. While there are multitudes of common stones that are hardly worth the effort to carry, there are a plethora of rarer and wildly valuable gems spread throughout. Though magic items in Basalt Dragon hoards are very rare, when they do appear they are usually some kind of jewelry, most definitely collected as a whole on accident by the dragon merely looking for the gems it prizes.

Basalt Dragons are solitary creatures, though they are never ones to shy away from worship from kobolds who they occasionally use to spread rumors of their hoard to lure adventurers to their doom.

A Basalt Dragon has been rumored to have moved into a coastal outcropping near a port town. While it has not bothered the residents in months, the townsfolk cannot keep the thought of that giant gemstone bounty out of their minds, or out of their conversations in the tavern. Adventurers could just be looking for an epic payday or are on the hunt for a specific gem encrusted object that fits the dragon’s MO. Kobold sightings and seismic activity could let the adventurers know they’re getting closer, or local fishermen may have tales of certain coastal caves occasionally emitting a faint glow long into the night.

A fall from a great height is one of the most common hazards facing an adventurer. At the end of a fall, a creature takes 1d6 bludgeoning damage for every 10 feet it fell, to a maximum of 20d6. The creature lands prone, unless it avoids taking damage from the fall.