Ancient Obsidian Dragon

The Obsidian dragon often will live in or around an active volcano, often preferring the ease it provides in creating just the perfect environment for their combustive tendencies. However, when an obsidian dragon does not feel lazy or they wish to announce their arrival on the mortal plane, the dragon will either go to find a dead volcano or claim a castle, turning it into a hellish landscape and torturing the earth with their psionic energies to make it more towards their liking. Their attitudes make them natural enemies of many gems who live in the same territory, as well as red and silver dragons.

Lair actions

On initiative count 20 (losing initiative ties), the dragon takes a lair action to cause one of the following effects:

• A large wave of flame rolls through the dragon's lair, igniting and incinerating any foolish enough to assault the wyrm in its home. The dragon creates a 100ft long, 20ft wide wave of flames within its sight, forcing all creatures within it to make a DC 15 dexterity saving throw. On a failed save, a creature is dealt 16 (3d10) fire damage and ignited. An ignited creature takes 1d10 fire damage at the beginning of their turn, and can end the ignition on themselves or another creature as an action or by moving through water. On a successful save a creature is not ignited.
• A wall of molten magma erupts from the earth, blasting creatures in its path away, and scorching those that remain. Five sections of magma rip from the ground, each one measuring 10ft long, 30ft tall and 2 ft wide. This wall can pass through spaces occupied by creatures, forcing them to make a DC 15 strength saving throw. On a failed save, the dragon chooses which side of the wall the creature ends up on, on a success the creature chooses which side they want to be on. Any creature that starts their turn within 10ft of this wall is dealt 11 (2d10) fire damage. Moving through this wall takes an action, and creatures that do so are dealt 33 (6d10) fire damage.

• Toxic vents rip open in the earth, spilling their sickening, nauseous gasses into the air. Creatures in three 10ft spheres must make a DC 15 constitution saving throw. On a failed save a creature is poisoned for up to one minute. A poisoned creature may not take the dash action, and may attempt to make the saving throw at the beginning of the turn to end the poisoned condition.

Regional Effects

A legendary obsidian dragon's lair is warped by the dragon's magic, which creates one or more of the following effects:

• Within 5 miles of their lair, a black, billowing cloud of soot constantly pours from the heart of the obsidian dragon's abode. This marks the edge of what it considers its private territory, and the land under this unnatural blanket is covered in a lair of soot that makes intruders easy to track, and which kills plant life rather thoroughly. This cloud fully disperses a month after the obsidian dragon's death.
• Within a mile of the dragon's lair, the land is ripped open and a hellish red glow comes from the rending wounds in the earth. Much of the land is caked in cooling obsidian and basalt, with other volcanic rock constantly oozing from new rends that appear without warning. Literal waterfalls of lava are a common sight, and there is no sign that any of the pyroclasmic activity will ever come to an end. Only after the dragon has been dead for a year will the most obvious displays peter to a stop, and any volcano that housed the dragon will remain active for up to a century, even if it had been dead before the obsidian dragon made it their lair.

• Within the lair itself, portals to Hell, Hades, the Abyss and the elemental plane of Fire can sometimes be found. Often used by the dragon just to call forth body guards, they also provide a way of escape if they need one from invading dragons or heroes. Demons, devils, yuggoloths and elementals can all be summoned by the dragon via these portals, and all of them are considered friendly and at least mostly loyal to its cause. While sometimes the dragon lets rival varieties of fiends fight one another for its amusement, or for the amusement of a prospective red or obsidian mate, the various minions it can call are typically kept under tight control and no attempts to continue the Blood Wars are allowed within the dragon's hold. These creatures will remain after the dragon's death until they are actually slain.