Purple dragons, also known as deep dragons, are the least well known of the chromatic dragons. Dwelling deep in the Underdark, most surface creatures have no knowledge of their existence.  They are well known to the drow, though; and vise versa.  Purple dragons often establish lairs near drow settlements.

Partially due to most creatures inexperience with them, and partially due to their formidable adaptations to life in the Underdark, purple dragons are some of the most dangerous of the chromatic dragons.  While physically not as impressive as other chromatic dragons, they boast a wider, more versatile range of abilities.  They posses multiple breath weapons, and the ability to shapechange, abilities usually attributed solely to metallic dragons, a misconception that the clever purple dragons are quick to exploit.

Deep Delvers. Purple dragons have a love of exploration and travel.  They spend most of their time exploring the endless depths of the Underdark and seeking out lore of exotic faraway places above ground where they dare not venture.  Though most of their time is spent getting further and further away from their lair, they always find their way back, following strong homing instincts to return to their hoard.

Puppet Masters. Purple dragons are incredibly intelligent.  They are masters at gathering and exploiting information to manipulate other creatures.  Unlike the green dragon, which manipulate through charm and force of personality, purple dragons do so through blackmail and cunning.  They are masters at analyzing other creatures, reading faces for tells, interpreting body language, and using their natural stealthiness to spy on targets.

Dark Shadows. Though they prefer the albino, sightless fish that populate the underground rivers and seas of the Underdark, they will hunt virtually any living creature they come across.  They prefer to stalk their prey, watching and waiting from the darkness, their dark coloration and sleek physique helping them to blend in with their surrounding, making them difficult to spot even for creatures with darkvision.

As with most natives to deep places, sunlight is a purple dragon's bane.  But that doesn't mean they confine themselves to the Underdark.  They leave it quite often, plane shifting to the Shadowfell.  Their psychic inclination and affinity for dark energies leaves them perfectly adjusted for travel through the Plane of Shadow.

Purple dragons often make their nests near areas infested with the undead, or lure them to their lairs in the hopes that their eggs might be influenced by the negative energy radiating from them.  Most often, it does, granting the next generation the ability to plane shift to the Shadowfell.  In some rare cases, the exposure to negative energy from undead gathered by its parent and the mutagenic faerzress energies of the Underdark causes a purple dragon wyrmling to hatch as a shadow dragon.

Variant: Purple Shadow Dragon Wyrmling

Exposure to negative energy may cause a purple dragon's egg to hatch as a shadow dragon.  A purple shadow dragon wyrmling is Challenge Rating 4 (1,100 XP) and gains the following traits:

Living Shadow. While in dim light or darkness, the dragon has resistance to damage that isn’t force or radiant.

Shadow Stealth. While in dim light or darkness, the dragon can take the Hide action as a bonus action.

Additionally, a purple shadow dragon wyrmling gains the following breath weapon:

Shadow Breath. The dragon exhales shadowy fire in a 15-foot cone. Each creature in that area must make a DC 11 Dexterity saving throw, taking 21 (6d6) necrotic damage on a failed save, or half as much damage on a successful one. A humanoid reduced to 0 hit points by this damage dies, and an undead shadow rises from its corpse and acts immediately after the dragon in the initiative count. The shadow is under the dragon’s control.

A purple dragon’s permanent lair is a honeycomb of rocky hollows connected by narrow, winding tunnels. Many tunnels lead to dead ends or traps and require real feats of exploration for anyone new to the lair to find a way through. Sometimes purple dragons make their lairs in the structures of previous Underdark residents, if the chambers and connecting hallways are elaborate enough for the dragons’ taste. They have a habit of luring undead, most commonly shadows, specters and wraiths, into their lairs, or nesting in areas heavily contaminated with faerzress (magical radiation found in the Underdark), making their lairs outright hostile environments for most living things.

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 causes magical radiation to flair up in a 30-foot-radius sphere centered on a point it can see within 120 feet of it, which lasts until the next initiative count 20.  When a creature moves into the spell’s area for the first time on a turn or starts its turn there, that creature must succeed on a DC 15 Constitution saving throw or take 22 (4d10) necrotic damage, and it suffers one level of exhaustion and emits a dim, greenish light in a 5-foot radius. This light makes it impossible for the creature to benefit from being invisible, and causes it to have disadvantage on Dexterity (Stealth) checks. The light caused by this lair action goes away on the next initiative count 20.  Constructs and undead are immune to the necrotic damage, but are still subjected to the light effect
• Magical darkness spreads from a point the dragon chooses within 60 feet of it, filling a 15-foot-radius sphere until the dragon dismisses it as an action, uses this lair action again, or dies. The darkness spreads around corners. A creature with darkvision can’t see through this darkness, and no light, magical or otherwise can illuminate it. Creatures within the area are blinded.  Creatures with blindsight, tremorsense, or truesight, or that do not rely on sight are unaffected.
• One creature the dragon can see within 120 feet of it must succeed on a DC 15 Charisma saving throw or be banished to the Shadowfell.  On the next initiative count 20, the creature reappears in the space it left or in the nearest unoccupied space if that one is occupied.  If the creature is not undead, it takes 28 (8d6) necrotic damage when it reappears.

Regional Effects

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

• The land within 6 miles of the lair takes twice as long as normal to navigate, as the caves and passageways of the Underdark seem to shift endlessly.
• The dragon can establish a telepathic link with any creature it is aware of within 6 miles of its lair, provided that creature can understand a language. An unwilling creature must make a DC 15 Intelligence saving throw to block the telepathic link.
• Any creature which falls asleep within 1 mile of the dragon's lair is afflicted with terrible nightmares, and must make a DC 15 Wisdom saving throw. On a failed save, the creature suffers a nightmare that lasts the duration of the target's sleep and prevents the target from gaining any benefit from that rest.  In addition, when the target wakes up, it takes 10 (3d6) psychic damage. Creatures that don't sleep, such as elves, are unaffected.

If the dragon dies, its telepathic link(s) end immediately, but all other effects fade over 1d10 days.