Ancient Amethyst Dragon.

The most serious of the Mineral Dragons, the Amethyst dragon lives a serious life where it sets goals for itself to complete, when it fails to complete a important goal, it tends to rampage through its domain, striking the entire land with lightning. The dragon is surrounded by almost unnoticeable earthy smoke scent. Its eye burn a lightning blue with a dark purple center. The Scales of the Amethyst Dragon are a bright purple, gem-like with a light blue tint along the edges. Its webbed feet and strong wings help it swim through swamp water with ease. 

Swamp and Desert Masters. Amethyst Dragons prefer to make their lairs and domains inside swamp caves or inside stormy mountains, sometimes it will even rest under swamp lakes and mud to clean itself. They also make their lairs in deserts where thunder storms plague their domain, in the stone caverns of the lair they lay resting under the sands, only coming out for food, treasure or to patrol its domain above the clouds inside the storm.

Shocking Eaters. Amethyst dragons actually hunt by shocking its prey with their lightning breath. These dragons will even sometimes eat lightning which causes its Amethyst crystals on its body to glow. 

Amethyst dragons make their lairs in lightning filled places, using their lightning breath and their burrowing ability to carve out crystallized caverns and tunnels beneath the sands, mountains or swamps. Thunderstorms rage around a legendary amethyst dragon’s lair, and narrow tubes lined with purple glowing crystals ventilate the lair, all the while avoiding the amethyst spikes that are the dragon’s first line of defense. A amethyst dragon's lair will collapse when the dragon dies, sinkholes throughout the maze like lair can be the death of many 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:

• The dragon chooses a point on where an amethyst is located in its lair. Crystal spikes sprout from the ground in a 20-foot radius centered on that point, each creature must make a DC 15 Dexterity saving throw or take  21 (6d6) piercing damage if hit with the tip of the crystal, bludgeon damage if hit with the edge of the crystal or if within 5ft of the crystal take force damage. 
• Lightning arcs, forming a 5-foot-wide line between two of the lair’s solid surfaces that a amethyst is located. They must be within 120 feet of the amethyst and 120 feet of each other. Each creature in that line must succeed on a DC 15 Dexterity saving throw or take 10 (3d6) lightning damage.
• A thunderclap originates at a point within 120 feet of a amethyst. Each creature within a 20-foot radius centered on that point must make a DC 15 Constitution saving throw or take 5 (1d10) thunder damage and be deafened until the end of its next turn.

Regional Effects

The region containing a legendary amethyst dragon’s lair is warped by the dragon’s magic, which creates one or more of the following effects:

• The lair is surrounded by glowing purple crystals (If a creatures bare skin touches the crystals take 1d4 lightning damage), these crystals create a light in a 5ft radius, and the dragon has the ability to see out of these crystals.
• Thunderstorms rage within 6 miles of the lair.
• Within its lair, the dragon can set illusory sounds, such as soft music and strange echoes, so that they can be heard in various parts of the lair.
• 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 Amethyst Dragon dies, these effects fade over the course of 1d10 days.