Making their lairs in the depths of the Underdark, deep dragons are nightmarish cousins of chromatic dragons. The warped magical energy of their subterranean realm gives them the ability to exhale magical spores that instill fear and scar the mind.

Deep dragons’ black-and-gray hide is smooth like a salamander’s, and their eyes are pale. As they age, their spore breath causes fungi to bloom across their skin, especially around the head and neck. Their wings are attached to their front legs and can fold in close to the body, allowing deep dragons to easily maneuver through relatively narrow tunnels.

Deep dragons often hoard secrets, delighting in knowledge of far-off lands. Many seek out new insights and tricks that they can use against other denizens of the Underdark, preferring social manipulation and crafty dealmaking to exerting themselves in combat. Deep dragons look down on any creature that isn’t useful to them, though they are willing to bargain for knowledge they lack.

Deep Dragon Lairs

Deep dragons’ lairs serve as bases for the dragons’ explorations, as well as providing safe storage for their hoards. When these curious creatures are away from home searching out new environments and seeing new vistas, they usually leave their lairs protected by servitors, allies, magic, traps, or some combination of these protections.

Deep Dragon Lair Features

A deep dragon lair might share the same basic structure as the sapphire dragon lair shown on map 5.12, but instead of being formed from stone, it might consist of chambers hollowed out within a fungus network growing near an underground river. Whatever the setup, a deep dragon festoons the narrow, twisting passages between the lair’s fungal walls with magical and mundane traps. A typical lair has the following features:

Connecting Passages. Because a deep dragon lacks a sapphire dragon’s ability to shape stone, add a few connecting passages or secret doors to otherwise inaccessible chambers, possibly including connections to the adjacent underground stream as entrances to the lair.

Reception Hall. The dragon uses one of the large chambers in the lair as a reception hall for allies and servitors. Like the rest of the lair, this chamber is lit by phosphorescent fungal blooms that give off soft green, blue, and purple light.

Hoard Chamber. The dragon’s hoard is hidden away in a more remote chamber, draped in illusion spells and protected by traps and magical alarms. When triggered, those alarms summon the dragon’s minions and allies first, followed by the dragon.

Underground River. Where an underground river runs along the outside edge of the lair, the dragon has slowed its flow with a rocky dam, creating a small pool in which to bathe and raise aquatic delicacies.

Guest Suite. A large chamber with connected smaller chambers, such as that seen toward the bottom of the map, forms a suite used as guest lodgings for visiting dragons. Though any treasures with significant financial or sentimental value to the host dragon are stored away in the protected hoard, these tastefully appointed visitors’ chambers contain lesser treasures from inaccessible or storied locales, chosen to pique visitors’ curiosity and provide an excuse for the host to tell these items’ tales.

A Deep Dragon’s Lair

Deep dragons make their lairs in well-hidden caves or sunless beaches in the Underdark, and these sites are often inaccessible without the ability to fly or dive underwater. They fill their lairs with secret passages and hiding places that allow them to escape or ambush visitors if the need arises. A well-cultivated lair abounds with Underdark fungi and plants, with the floor, walls, and ceiling covered in carpets of mold and moss, or featuring larger mushrooms and plants in neatly organized displays.

The challenge rating of a legendary deep dragon increases by 1 when it’s encountered in its lair.

Shadow Dragon Lairs

When dragons become aware of the Shadowfell’s malign influence seeping into their territories, most scoop up their hoards and abandon any compromised lairs. But some are stubborn, prideful, or bitter enough to stay, even in the face of inevitable corruption. More often, a dragon is unknowingly swept up by the Shadowfell while asleep, awakening after a years-long rest to find that both dragon and lair have changed. In these cases, a shadow dragon’s lair undergoes the same transformation as the dragon, becoming a shadowy, melancholic version of the original site.

Shadow dragons that are born on the Shadowfell or seek out new lairs after their transformations establish lairs according to the preferences of their kind, though they find comfort only in the most gloomy and cheerless of places. Reconciling these sometimes-contrasting urges can lead to some very unusual lair choices.

As an example, consider the red dragon lair in map 5.11 as the lair of a red shadow dragon. In this case, the once-active volcano has now lapsed into dormancy. Its lava flows have cooled into a blackened, alien landscape. Ash coats the slopes of the caldera, picked up by the weird swirling winds common to this region and drawn into the atmosphere. Clouds of ash periodically cast the surrounding lands into deep shadow, before the fine grit once again falls to the ground in a hazy gray blizzard. The shadow dragon prowls the region during these hazes, rendered all but invisible by the eddies of ash.

In the heart of the lair, even the brightest light is muted, and creatures find their eyes playing tricks on them as details and distance are distorted. The shadow dragon rarely leaves this place except to hunt and is attended by dozens of shadows.

Lair Actions

On initiative count 20 (losing initiative ties), the dragon can take one of the following lair actions; the dragon can’t take the same lair action two rounds in a row:

Deep Torpor. The dragon casts the slow spell, requiring no spell components and using Charisma as the spellcasting ability (spell save DC 16). The spell ends early if the dragon uses this lair action again or if the dragon dies.

Mossy Sludge. The dragon conjures sludge-like moss that briefly covers surfaces in the lair. The ceiling, floor, and walls of the lair become difficult terrain until initiative count 20 on the next round.

Toxic Spores. The dragon fills a 20-foot cube it can see within 120 feet of itself with toxic spores. Each creature in that area must succeed on a DC 15 Constitution saving throw or take 14 (4d6) poison damage and be poisoned until the end of its next turn.

Shadow dragons have access to the lair actions usable by untransformed dragons of the same kind. The effects of these actions might be cosmetically altered, seeming darker, gloomier, and more subdued. They might also deal necrotic damage instead of other damage types. At your discretion, a legendary (adult or ancient) shadow dragon can use the following additional lair action while in its lair:

Banish Light. Any nonmagical source of illumination within a 60-foot-radius sphere centered on the dragon is snuffed out, and any spell that creates light within that same area is dispelled.

Regional Effects

The region surrounding a legendary deep dragon’s lair is altered by the dragon’s magic, creating one or more of the following effects:

Preservation of Knowledge. Books, letters, and any other physical forms of writing within 6 miles of the dragon’s lair become magically charged and can’t be damaged by nonmagical means.

Restless Sleep. When a creature finishes a long rest within 6 miles of the lair, the creature must first succeed on a DC 10 Constitution saving throw or be unable to reduce its level of exhaustion. Creatures immune to the poisoned condition are immune to this effect.

Verdant Growth. Vegetation and fungi within 6 miles of the dragon’s lair grow faster and cover a greater area than they normally would. Foraging in this area yields twice the usual amount of food.

When a shadow dragon establishes a lair on the Material Plane, the region around the lair takes on some of the characteristics of the Shadowfell, creating one or more of the following effects:

Brooding Despair. Creatures within 1 mile of the dragon’s lair that have an Intelligence score of 5 or higher feel forlorn and hopeless.

Dying Light. Light is diminished within 6 miles of the dragon’s lair, lightly obscuring the land in gloomy shadows.

Gloomy Portals. Some caves, caverns, pits, and other places of deep gloom within 1 mile of the dragon’s lair form portals to the Shadowfell, allowing creatures from that plane to dwell nearby.

If the dragon dies, these effects fade over the course of 1d10 days.