Ancient Sea Serpent

Ancient Sea Serpent CR: 14

Gargantuan dragon, neutral

Armor Class: 17 (natural armour)

Hit Points: 170 11d20+55

Speed: 20 ft , swim: 60 ft

STR

24 +7

DEX

15 +2

CON

20 +5

INT

13 +1

WIS

16 +3

CHA

12 +1

Saving Throws: Str +12, Con +10

Skills: Perception +8, Stealth +7

Damage Immunities: Cold

Senses: Darkvision 120 ft, passive Perception 18

Languages: Common, Draconic

Challenge Rating: 14

Amphibious. The sea serpent can breathe air and water.
Legendary Resistance (2/Day). If the sea serpent fails a saving throw, it can choose to succeed instead.
Siege Monster. The sea serpent deals double damage to objects and structures.

Actions

Multiattack. The sea serpent makes one Bite attack and one Constrict or Tail attack.
Bite. Melee Weapon Attack +12 to hit, reach 15 ft, one target. Hit 20 [2d12+7] piercing damage plus 6 1d12 cold damage.
Constrict. Melee Weapon Attack +12 to hit, reach 20 ft, one creature. Hit 29 4d10+7 bludgeoning damage, and the target is grappled (escape DC 20). Until this grapple ends, the target is restrained, and the sea serpent can't constrict another target.
Tail. Melee Weapon Attack +12 to hit, reach 20 ft, one target. Hit 13 1d10+7 bludgeoning damage. If the target is a creature, it must succeed on a Strength DC 20 saving throw or be pushed up to 30 feet away from the sea serpent and be knocked prone.
Rime Breath (Recharge 5-6). The sea serpent exhales a 60 ft cone of cold. Each creature in that area must make a DC 18 Constitution saving throw, taking 49 9d10 cold damage on a failed save, or half as much damage on a successful one.

Legendary Actions

The sea serpent can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only one at the end of another creature's turn. The sea serpent regains spent legendary actions at the start of its turn.

• Tail. The sea serpent makes one Tail attack.
• Bite (Costs 2 Actions). The sea serpent makes one Bite attack.

Ancient sea serpents, at least stories of them, are found throughout the world. They attack ships by ramming them, or plucking sailors of the ship. They have a freezing breath attack, and can be found in lakes (usually where there is access to the sea). Aggressive and territorial, they defend their territory from dragon turtles, and other gargantuan sea monsters regularly. Like any dragon-kin they amass fortunes, usually sailors trinkets, booty, and trade goods. Each sea serpent lair is an underwater cave, a sunken castle or equivalent, or a sunken ship. They have large crests running down the length of their bodies from the back of their heads, and generally no limbs.

Suggested Environments

Seas & larger lakes.