Descent's from true dragon you can live for 200 years and mature at the age of 18. Though when the crystal dragons reach the age of 200 there body the next day will completely be encased in crystal and glow as a crystal providing light in caves. After thousands of years the crystal dragon can be reborn the crystal that they were incased in will stop glowing and if dug below the crystal a egg can be found. After the egg is found and allowed to be close to a warmth will hatch in 2 days.

Your size is medium. Your height is 7 - 8 ft.

Your base walking speed is 30 feet.

Your know Draconic, Deep speech, Common and Gaelic.

Your species is Neutral.

You see in a blue hue in the darkness. Can see 60ft in dim light like it is bright light.

Since this species of Dragon has been absent from the surface world for a long time once sex has been the constant. 

Due to your draconian heritage you are hearty and strong from being underground.

You can use your action to exhale crystal's that deal bludgeoning. When you use your breath weapon, each creature in the area of the exhalation must make a saving throw, In a 15-foot cone. The DC for this saving throw equals 8 + your Constitution modifier + your proficiency bonus. A creature takes 2d6 damage on a failed save, and half as much damage on a successful one. The damage increases to 3d6 at 6th level, 4d6 at 11th level, and 5d6 at 16th level. After you use your breath weapon, you can’t use it again until you complete a short or long rest. The crystal's explode on impact dealing 2d4 fire and 1d4 cold.

Due to you being under ground you have resistance to Bludgeoning damage. Rock falls are common so your people have adapted.