Amphibious. The sea serpent can breathe air and water.

Keen Scent. This sea serpent can notice creatures by scent in a 180-foot radius underwater and can detect blood in the water at a range of up to a mile.

Legendary Resistance (3/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 can use its frightful presence and make two attacks: one with its bite and one with its tail.

Bite. Melee Weapon Attack: +19 to hit, reach 20 ft., one target. Hit: 45 (10d6 + 10) piercing damage and 28 (8d6) poison damage.

Ram. Melee Weapon Attack: +19 to hit, reach 10 ft., one target. Hit: 65 (10d10 + 10) bludgeoning damage.

Tail. Melee Weapon Attack: +19 to hit, reach 30 ft., one target. Hit: 37 (6d8 + 10) bludgeoning damage.

Frightful Presence. Each creature of the sea serpent’s choice that is within 120 feet of the sea serpent and aware of it must succeed on a DC 23 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’s saving throw is successful or the effect ends for it, the creature is immune to the sea serpent’s Frightful Presence for the next 24 hours.

Capsize. If the sea serpent moves at least 30 feet straight toward a watercraft (boat, ship, ferry, etc.) and then hits it with a ram attack on the same turn, there is a chance that it will capsize. All occupants of the watercraft must make Dexterity saving throw when the craft is rammed (see below). To determine if the watercraft capsizes, consult the following table:

• Small The craft is destroyed, all on board must make a successful DC 23 Dexterity saving throw to avoid being stunned. On a failed save, passengers each take 65 (10d10 + 10) bludgeoning damage, are trapped in the wreckage, and are stunned for 1 minute, or half as much on a successful save and are thrown clear of the wreckage.
• Medium The craft must make a generic DC 20 saving throw to avoid being destroyed. If the craft fails the save by 5 or more, it capsizes and all on board must make a DC 18 Dexterity saving throw to avoid being pulled under with the ship. If the save is successful, the ship takes 120 (20d10 + 10) damage and those on board must make a successful DC 17 Dexterity saving throw. On a failed save, the passenger takes 48 (7d10 + 10) bludgeoning damage and is knocked prone (or overboard if they are near the ship’s edge), or half as much without being knocked prone on a success.
• Large The craft must make a generic DC 18 saving throw to avoid being capsized. If it fails the save by 5 or more, the ship capsizes and all on board must make a DC 16 Dexterity saving throw to avoid being pulled under with the ship. If the save is successful, the ship takes 103 (17d10 + 10) damage and those on board must make a DC 14 Dexterity saving throw. On a failed save, the passenger takes 37 (5d10 + 10) bludgeoning damage and is knocked prone (or overboard if they are near the ship’s edge), or half as much without being knocked prone on a success.
• Huge The craft must make a generic DC 16 saving throw to avoid being capsized. If it fails the save by 5 or more, the ship capsizes and all on board must make a DC 15 Dexterity saving throw to avoid being pulled under with the ship. If the save is successful, the ship takes 81 (13d10 + 10) damage and those on board must make a DC 12 Dexterity saving throw. On a failed save, the passenger takes 26 (3d10 + 10) bludgeoning damage and is knocked prone (or overboard if they are near the ship’s edge), or half as much without being knocked prone on a success.
• Gargantuan The craft must make a generic DC 14 saving throw to avoid being capsized. If it fails the save by 5 or more, the ship capsizes and all on board must make a DC 13 Dexterity saving throw to avoid being pulled under with the ship. If the save is successful, the ship takes 65 (10d10 + 10) damage and those on board must make a DC 10 Dexterity saving throw. On a failed save, the passenger takes 15 (1d10 + 10) bludgeoning damage and is knocked prone (or overboard if they are near the ship’s edge), or half as much without being knocked prone on a success.

Legendary Actions

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

Detect. The sea serpent makes a Wisdom (Perception) check.

Tail Attack. The sea serpent makes a tail attack.

Breach (Costs 3 Actions). The sea serpent dives deep below the surface of the water then swims rapidly upward, propelling itself out of the water, often clearing the surface, before violently slamming into the surface with great force. Each creature within 60 feet of the sea serpent must succeed on a DC 23 Dexterity saving or take 27 (5d10) bludgeoning damage and be knocked prone.

gargantuan

dragon

cr30

tome-of-horrors

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