Purple Dragon

Deep dragons, also called purple dragons, drakes of the depths, and silent hunters, were a type of chromatic dragon that lived in the Underdark. Despite their large size, deep dragons were slender and agile, and their snakelike bodies, narrow wings, and thin limbs allowed them to crawl through the tunnels of the Underdark. Their scales were smooth, and in the light, an adult dragon's scales were the color of amethyst, while in the dark, they appeared nearly black. In general, older specimens had much darker scales, while younger ones had more purple or maroon coloration. Older deep dragons were known to develop fungal growths around their heads and necks.
A dragon egg could be identified as that of a deep dragon by the purple tinge seen when held in front of an intense white light, though it shared this trait with shadow dragon and amethyst dragon eggs.
Deep dragons were patient and cunning. They prioritized their own survival above all else, yet were known to relish the opportunity to hunt or even fight if the situation demanded it. They preferred to manipulate and negotiate rather than to risk combat, and were crafty dealmakers. They were quick to disregard any creature that wasn't useful to them.
Deep dragons collected trivia, insights, tricks, and knowledge from far flung places, and delighted in acquiring new information. They were known to collect magic items, not simply to hoard but also to use for themselves. Some deep dragons enjoyed assuming the form of drow and infiltrating the dark elves' cities in disguise. In order to better allow them to navigate the narrow underground tunnels which they called home, deep dragons developed potent innate magical powers, including the ability to transmute rock to mud, and to cast spells like passwall, freedom of movement, and stone shape.
Perhaps their most distinctive ability was their unique shapechanging power which developed as they aged. The first form they learned to adopt was that of a winged snake, which did not reduce their overall size but allowed them to slither and fly unimpeded by extra limbs. The second form they learned to adopt was that of a normal humanoid, and they could alter this form's appearance as with a polymorph self spell.
Deep dragons were incapable of becoming intoxicated.
The claws of a deep dragon were intended to dig through solid rock, and as such, were devestating in combat even against heavily armored enemies. They preferred to pick off their enemies strategically, stalking them in the dark before pouncing or triggering a rockfall to bury them.[5]
A deep dragon's breath weapon attacked creatures' minds, and caused the target to be dazed or dominated, depending on the strength of the wyrm. These effects were attributed to fungal spores that the dragon exhaled. They were also known to be able to breath a cone of gas that was caustic to flesh.
Deep dragons were harmed by direct sunlight.
Purple dragons inhabited the Underdark, and were rarely known on the surface. However, younger specimens were known to occasionally venture upward, generally with some mission to claim a treasure or exact revenge on a foe, but sometimes just for the sake of exploration. Young deep dragons rarely left the lairs of their parents until they had mastered both their serpentine and humanoid alternative forms.
Lairs were located in the Upperdark and Middledark, usually no deeper than 7 miles (11 kilometers), and were highly idiosyncratic: some were built within ancient ruins, others on the shores of underground lakes, and others were carved out of masses of living fungus. Regardless, most of these lairs were full of secret passages to allow the dragon to make quick escapes and to prepare surprise ambushes. Lairs were often difficult to access, even for the dragon itself without using its serpentine or humanoid form, and were filled with traps and servants to protect the dragon's hoard, especially for times when the dragon ventured out to seek new information or treasures. They were known to transplant dangerous specimens of fungi into their lairs to serve as traps, and in general, underground varietals of fungi often abounded around deep dragons' lairs and even on their bodies. Their magic, and this somewhat symbiotic relationship with underground fungus, was said to be a result of their species' exposure to the pervading magic of the Underdark.