b'Cave Dragon, Ancient \n'b'  Gargantuan   dragon ,  neutral evil  \n'b'  Armor Class  20 (natural armor)  Hit Points  507 (26d20 + 234)  Speed  40 ft., burrow 40 ft., climb 40 ft.\n'b' STATS STR: 30 (+10) DEX:  12 (+1)  CON:  29 (+9)  INT:  14 (+2)  WIS:  16 (+3)  CHA:  18 (+4)  \n'b'\n'b'\n'b'\n'b'\n'b'\n'b'\n'b'  Saving Throws   Dex  +9,  Con  +17,  Wis  +11,  Cha  +12  Skills   Perception  +19,  Stealth  +9  Damage Immunities  poison  Condition Immunities   blinded ,  poisoned   Senses  blindsight 60 ft., tremorsense 120 ft., passive  Perception  29  Languages  Common, Darakhul, Draconic  Challenge  25 (75,000 XP)  Proficiency Bonus  +8 \n'b' SPECIAL TRAITS \n'b'\n'b'  Darkness Aura . The cave dragon emits magical  darkness  in a 30-foot radius around it. The  darkness  moves with the dragon and spreads around corners.  Darkvision  can\xe2\x80\x99t penetrate this  darkness , and no natural light can illuminate it. If any of the darkness overlaps with an area of light created by a spell of 4th level or lower, the spell creating the light is dispelled. At the start of each of its turns, the dragon chooses whether this aura is active. A successful  dispel magic  (DC 15) cast on the dragon suppresses this aura for 1 minute. \n'b'  Legendary Resistance (3/Day) . If the dragon fails a saving throw, it can choose to succeed instead. \n'b'  Magical Tunneler . The cave dragon can burrow through any unworked earth and stone. While doing so, the dragon can choose whether to leave the material it moves through undisturbed or leave a 15-foot diameter tunnel in its wake. \n'b'  Spiked Climb . The dragon uses its spikes to hold itself in place while climbing, allowing it to climb difficult surfaces, including upside down on ceilings, without needing to make an ability check. If it climbs upside down on a ceiling or suspends itself on a vertical surface while leaving its claws free, it can\xe2\x80\x99t use the Ruff Spikes  reaction . \n'b'\n'b' ACTIONS \n'b'\n'b'  Multiattack . The dragon uses its Frightful Presence. It then makes three attacks: one with its Bite and two with its Claws. \n'b'  Bite .  Melee Weapon Attack : +18 to hit, reach 15 ft., one target.  Hit : 21 (2d10 + 10) piercing damage plus 14 (4d6) poison damage. \n'b'  Claw .  Melee Weapon Attack : +18 to hit, reach 10 ft., one target.  Hit : 17 (2d6 + 10) slashing damage. \n'b'  Tail .  Melee Weapon Attack : +18 to hit, reach 20 ft., one target.  Hit : 19 (2d8 + 10) bludgeoning damage. \n'b'  Frightful Presence . Each creature of the dragon\xe2\x80\x99s choice that is within 120 feet of the dragon and aware of it must succeed on a DC 20  Wisdom  saving throw or become  frightened  for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature\xe2\x80\x99s saving throw is successful or the effect ends for it, the creature is immune to the dragon\xe2\x80\x99s Frightful Presence for the next 24 hours. \n'b'  Poison Breath (Recharge 5\xe2\x80\x936) . The dragon exhales a cone of black, poisonous gas in a 90-foot cone. Each target in that area must make a DC 25  Constitution  saving throw. On a failure, a creature takes 91 (26d6) poison damage and is  poisoned  until cured by the  greater restoration  spell or similar magic. On a success, a creature takes half the damage and isn\xe2\x80\x99t  poisoned . \n'b'\n'b' REACTIONS \n'b'\n'b'  Ruff Spikes . When a creature moves to a space within 10 feet of the cave dragon, the dragon flares its many feelers and spikes. The creature must succeed on a DC 25  Dexterity  saving throw or take 13 (3d8) piercing damage and be prevented from entering that space. \n'b'\n'b' LEGENDARY ACTIONS \n'b' The dragon can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature\xe2\x80\x99s turn. The dragon regains spent legendary actions at the start of its turn. \n'b'\n'b'  Detect . The dragon makes a  Wisdom  (Perception) check. \n'b'  Tail Attack . The dragon makes a Tail  attack . \n'b'  Limb Sweep (Costs 2 Actions) . The dragon sweeps its wingless limbs outward. Each creature within 10 feet of the dragon must succeed on a DC 25  Dexterity  saving throw or take 15 (2d6 + 8) bludgeoning damage and be pushed up to 10 feet away from the dragon and forced  prone . \n'b'\n'b' LAIR \n'b' Labyrinthine systems of tunnels, caverns, and chasms make up the world of cave dragons. They claim miles of cave networks as their own. Depending on the depth of their domain, some consider the surface world their territory as well, though they visit only to eliminate potential rivals. \n'b' On initiative count 20 (losing initiative ties), the dragon takes a lair action to cause one of the following effects; the dragon can\xe2\x80\x99t use the same effect two rounds in a row: \n'b'\n'b'  Cave-In . The ceiling collapses above one creature the dragon can see within 120 feet of it. The creature must make a DC 15  Dexterity  saving throw. On a failure, a creature takes 10 (3d6) bludgeoning damage and is forced  prone  and buried. On a success, a creature takes half the damage and isn\xe2\x80\x99t forced  prone  or buried. A buried creature is  restrained  and unable to breathe or stand up. A creature, including the buried creature, can take an action to free the buried creature by succeeding on a DC 15  Strength  check. \n'b'  Release the Vermin . A 20-foot radius sphere of insects appears centered on a point the dragon can see within 120 feet of it. When a creature enters the cloud of insects for the first time on a turn or starts its turn there, that creature must make a DC 15  Constitution  saving throw, taking 11 (2d10) piercing damage on a failed save, or half as much damage on a successful one. The cloud of insects lasts until initiative count 20 on the next round. \n'b'  Split the Earth . A crack appears in the ground within 120 feet of the dragon that is 10 feet long, 10 feet wide, and 20 feet deep. Each creature standing on a spot where the crack opens must succeed on a DC 15  Dexterity  saving throw or fall in, taking falling damage. A creature that successfully saves moves with the crack\xe2\x80\x99s edge as it opens. The crack remains open for 1 minute, until the dragon uses this lair action again, or until the dragon dies. \n'b'\n'b' REGIONAL EFFECTS \n'b' The region containing a legendary cave dragon\xe2\x80\x99s lair is warped by the dragon\xe2\x80\x99s magic, which creates one or more of the following effects: \n'b'\n'b'  Flight of the Beetles . Swarms of vermin within 1 mile of the lair increase in both  size  and number as their populations try to survive the dragon\xe2\x80\x99s undiscriminating hunger. \n'b'  Toxic Air . Once each hour, poisonous and odorless gases fill random passages and caverns for 1 minute, and just as quickly disperse, within 6 miles of the dragon\xe2\x80\x99s lair. \n'b'  Water Underground . Each time the dragon\xe2\x80\x99s temper flares, but no more often than once every 30 days, flash flooding turns tunnels into death traps as tremors create fissures in the stone within 6 miles of the lair. On the surface, ponds drain away, and long-dry creek beds break their banks in flood. If the dragon dies, these effects fade over the course of 1d10 days. \n'b'\n'b' ABOUT \n'b' Covered in black spikes, the dragon\xe2\x80\x99s eyeless head swings from side to side. Darkness creeps from its strange, eel-like hide, spreading like ink in water. \n'b' Apex predators of the underworld, cave dragons are the stuff of nightmare for creatures with little else to fear. They can speak, but they value silence, speaking rarely except when bargaining for food. \n'b'  Born to Darkness . Eyeless, these dragons have long, thin spikes that help them navigate tunnels or seal passages around them, preventing foes from outflanking them. Their stunted wings are little more than feelers, useful in rushing down tunnels. Their narrow snouts poke into tight passages, which their  tongues  scour free of bats and vermin. Young cave dragons and wyrmlings can fly, poorly, but older specimens lose the gift of flight. Cave dragon hide is more like eel skin than reptilian scales, and it grows mottled with brown and black as it ages. \n'b'  Ravenous Marauders . Cave dragons are always hungry and ready to eat everything. They devour undead, plant creatures, or anything organic. When feeding, they treat all nearby creatures as both a threat and the next course. Alliances they make only last so long as their allies make themselves scarce when the dragon feeds. They can be bribed with food as easily as with gold, but other attempts at diplomacy typically fail. Cave dragons do form alliances with peoples of the underworld, joining them in battle against enemies, but there is always a price to be paid in flesh, bone, and marrow. Wise allies keep a cave dragon well fed. \n'b'  A Hard Life . Limited food underground makes truly ancient cave dragons almost unheard of. The eldest tend to die of starvation after stripping their territory bare of prey. Their nigh-endless hunger leaves the ancients the most likely of cave dragons to form alliances, especially with allies that promise\xe2\x80\x94and deliver\xe2\x80\x94food. On occasion, cave dragons climb to the surface to feed, but their earthbound, plodding pace leaves them outcompeted by other predators or unable to keep up with swift or flying prey. They prefer tight tunnels where they can ambush and outmaneuver prey. \n'b'  Edible Hoards and Vertical Lairs . Due to the scarcity of food in their subterranean world, a cave dragon\xe2\x80\x99s hoard may consist largely of food sources:  bat  colonies, enormous beetles, carcasses in states of decay, a cavern infested with shriekers, and whatever else the dragon doesn\xe2\x80\x99t immediately devour. Cave dragons are fond of bones and items with strong taste or smell. \n'b' Vast collections of bones, teeth, ivory, and the shells of huge insects litter their lairs, arranged like artful ossuaries. Large vertical chimneys serve as nesting sites for eggs and are popular resting places when a cave dragon sleeps within its lair. Chimneys just wide enough to hold young cave dragons make preferred ambush sites, as the dragons\xe2\x80\x99 tough spikes  help  hold them in position until prey passes beneath. The oldest cave dragons also retreat to vertical chimneys near nesting sites or within their lairs to die in peace. Stories claim that enormous treasures are heaped up in these ledges, abysses, and other inaccessible locations.'