Gargantuan beast, neutral

Armor Class: 16 (natural armor)

Hit Points: 217 (15d20 + 60)

Speed: 20 ft , swim: 50 ft

STR

24 +7

DEX

14 +2

CON

19 +4

INT

3 -4

WIS

11 +0

CHA

11 +0

Saving Throws: Str +10, Con +7

Skills:

• Perception +4
• Stealth +6

Damage Resistances: Acid; Fire; Bludgeoning, Piercing, Slashing from nonmagical attacks

Damage Immunities: Cold

Condition Immunities: Charmed, Frightened, Grappled, Petrified, Prone

Senses:

• Darkvision: 120ft.
• Passive Perception: 14

Languages: None

Challenge Rating: 10

Actions

• Multiattack. The sea serpent makes two attacks: once with its bite and once with its constrict.
• Bite. Melee Weapon Attack: +7 to hit, reach 20 ft., one target. Hit: 22 (3d8 + 7) piercing damage.
• Constrict. Melee Weapon Attack: +7 to hit, reach 20 ft., one target. Hit: 19 (3d6 + 7) bludgeoning damage, and the target is grappled (escape DC 16). Until this grapple ends, the creature is restrained, and the sea serpent can’t constrict another target.
• Elusive Dive. The sea serpent takes the Dash action, and until the beginning of its next turn, it gains a +10 bonus on Dexterity (Stealth) checks and cannot be tracked by nonmagical means.

Legendary Actions

A sea serpent can take 1 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’s turn. A sea serpent regains spent legendary actions at the start of its turn.

• Detect (Costs 1 Action). The sea serpent makes a Wisdom (Perception) check.
• Surge (Costs 1 Action). The sea serpent swims its base movement rate, without provoking opportunity attacks.