b'Sea Dragon, Ancient \n'b'  Gargantuan   dragon ,  neutral evil  \n'b'  Armor Class  22 (natural armor)  Hit Points  518 (28d20 + 224)  Speed  40 ft., fly 80 ft., swim 80 ft.\n'b' STATS STR: 29 (+9) DEX:  10 (+0)  CON:  27 (+8)  INT:  19 (+4)  WIS:  17 (+3)  CHA:  21 (+5)  \n'b'\n'b'\n'b'\n'b'\n'b'\n'b'\n'b'  Saving Throws   Dex  +7,  Con  +15,  Wis  +10,  Cha  +12  Skills   Perception  +17,  Stealth  +7  Damage Immunities  cold  Senses  blindsight 60 ft., darkvision 120 ft., passive  Perception  27  Languages  Common, Draconic, Primordial  Challenge  23 (50,000 XP)  Proficiency Bonus  +7 \n'b' SPECIAL TRAITS \n'b'\n'b'  Amphibious . The dragon can breathe air and water. \n'b'  Legendary Resistance (3/Day) . If the dragon fails a saving throw, it can choose to succeed instead. \n'b'  Siege Monster . The dragon deals double damage to objects and structures. \n'b'\n'b' ACTIONS \n'b'\n'b'  Multiattack . The dragon uses its Frightful Presence. It then makes one Bite  attack  and two Fin attacks. \n'b'  Bite .  Melee Weapon Attack : +16 to hit, reach 15 ft., one target.  Hit : 20 (2d10 + 9) piercing damage plus 14 (4d6) cold damage. \n'b'  Fin .  Melee Weapon Attack : +16 to hit, reach 10 ft., one target.  Hit : 16 (2d6 + 9) slashing damage. \n'b'  Tail .  Melee Weapon Attack : +16 to hit, reach 20 ft., one target.  Hit : 18 (2d8 + 9) 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'  Tidal Breath (Recharge 5-6) . The dragon exhales a crushing wave of frigid seawater in a 90-foot cone. Each creature in that area must make a DC 23  Dexterity  saving throw. On a failure, the creature takes 44 (8d10) bludgeoning damage and 44 (8d10) cold damage and is pushed up to 45 feet away from the dragon and forced  prone . On a success, the creature takes half the damage and isn\xe2\x80\x99t pushed or forced  prone . \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'  Wing Attack (Costs 2 Actions) . The dragon beats its wings. Each creature within 15 feet of the dragon must succeed on a DC 24  Dexterity  saving throw or take 16 (2d6 + 9) bludgeoning damage and be forced  prone . The dragon can then move up to half its flying speed, or swimming speed if in the water. \n'b'\n'b' LAIR \n'b' Sea dragons dwell in lairs beneath the waves: ocean fissures and caves, lightless trenches full of strange rock formations, and sheltered reefs of cultivated coral. Whatever the place, it\xe2\x80\x99s dedicated to the worship of sea gods. Despite the draconic instinct for seclusion and protection when choosing a lair, sea dragons always choose lairs relatively close to humanoid trade routes and abundant supplies of fish. \n'b' The sky surrounding a sea dragon\xe2\x80\x99s lair is perpetually stormy, and the seas run high. If a captain is courageous, these high winds and swift-running currents can cut significant time off a voyage. \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'  Create Coral Wall . The dragon creates an opaque wall of living coral on a solid surface it can see within 120 feet of it. The wall can be up to 30 feet long, 30 feet high, and 1 foot thick. When the wall appears, each creature in its area is pushed 5 feet out of the wall\xe2\x80\x99s space on whichever side of the wall it wants, and it must make a DC 15  Dexterity  saving throw, taking 18 (4d8) slashing damage on a failed save, or half as much damage on a successful one. While the wall remains, any creature that touches the wall must also make the saving throw. Each 10-foot section of the wall has AC 5, 30  hp ,  resistance  to fire damage, and immunity to poison damage and psychic damage. The wall lasts until the dragon uses this lair action again or until the dragon dies. \n'b'  Invoke the Sea\xe2\x80\x99s Calm . The currents around up to four creatures in the water and that the dragon can see within 120 feet of it work against the creatures. Each target must succeed on a DC 15  Strength  saving throw or it can\xe2\x80\x99t use  reactions , its speed is halved, and it can\xe2\x80\x99t make more than one  attack  on its turn until initiative count 20 on the next round. \n'b'  Whirlpools . Four vortexes of water appear centered on points underwater or on the water\xe2\x80\x99s surface that the dragon can see within 120 feet of it. Each vortex takes the shape of a cylinder that is 30 feet tall with a 5-foot radius. Each creature that enters a vortex for the first time on a turn or starts its turn there must make a DC 15  Strength  saving throw or be  restrained . A creature, including a  restrained  creature, can take its action to free the restrained creature by succeeding on a DC 15 Strength check. The vortexes last 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 sea 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'  Chill of the Deeps . Water temperatures drop within 1 mile of the dragon\xe2\x80\x99s lair, turning the water frigid and endangering swimming creatures not accustomed to arctic waters. \n'b'  Tempestuous Weather . Storms and rough water are more common within 6 miles of the lair. \n'b'  Thriving Waterways . Sea life becomes richer within 6 miles of the lair. Schools of fish move into new waters, sharks become common, and whale migration paths shift to pass near the area. If the dragon dies, these effects fade over the course of 1d10 days. \n'b'\n'b' ABOUT \n'b' This aquamarine dragon has a shark\xe2\x80\x99s head that tapers off into a sleek eel-like body. Its large fins double as wings. \n'b'  Divine Dragons . Sea dragons are the children of the ocean and believe they are semi-divine beings, worthy of worship. \n'b' Given their size and power, they might be right; certainly, they are often companions or steeds to gods of the sea. Despite the solemn duties the sea dragons invoke thanks to their lineage, they are extremely whimsical. While these immense creatures are playful, their games can shatter hulls and drown sailors. The sea dragons course through the waves with tangible joy as they hunt whales and entire schools of tuna. \n'b'  Shipwreck Art . Sea dragons love collecting treasure. They especially prize the sunken, treasure-filled hulls of ships lost to storm, battle, or their own handiwork. While they appreciate all wealth, they prefer hardy items that stand up to long exposure to sea water. Precious metals and gemstones add a dramatic luster to the dragon\xe2\x80\x99s lair when they catch stray beams of light. \n'b' Sea dragons take more perishable treasures and place them on a reef-altar, to dissolve in the sea as a tithe to the sea gods. \n'b'  Sunken Memorials . A sea dragon\xe2\x80\x99s lair is littered with meticulously arranged ships consigned to the deeps. These wrecks are often artfully smashed to allow the treasures in the hold to spill out onto the sea floor. It may seem haphazard, but it displays a complex aesthetic that only other sea dragons can truly appreciate. Because they arrange these wrecks so carefully, a dragon notices immediately if its hoard is disturbed. \n'b'  Priests . Every sea dragon is devoted to the dragon god of the sea. As a result, many sea dragons use the innate spellcasting variant. \n'b' Sea dragons favor spells that manipulate water or the weather, emulate storms, deal lightning or cold damage, divine the future, or conjure sea creatures to fight alongside the dragon.'