Sea Serpent
These rare and gigantic creatures lurk in the depths of ocean trenches. A serpent has a lithe body of a snake, with fins and iridescent scales along the length of its form. The smallest sea serpents dwarf most sailing vessels and the largest are better thought of as islands than as beasts. Scholars believe that sea serpents never stop growing and that there is no effective limit to their size should they be able to find prey.
Bane of Ships. Sea serpents lay claim to vast areas of remote ocean. Any ship that encroaches one's territory can expect to be attacked. A sea serpent defending its territory will wrap itself around the offending vessel and slowly crush it; any sailors that attempt to prevent this fate are plucked off the deck and eaten alive. There are even a few recorded instances of serpents fighting with dragon turtles over territory. Thankfully, these battles are rare as the two creatures are unlikely to share habitats.
Eons of Growth. Sea serpents do not appear to age. Sea elf sages note that the same sea serpents that were known some 10 generations ago seem to still live and lair in the undersea caves and trenches where few dare to journey. Sea serpents do occasionally go into a form of torpor in which they lie dormant at he bottom of the ocean for years. Older and larger the serpents spend more time in dormancy than their younger kin. It is an unfortunate explorer that upon finding a new island realizes instead that they are instead on the back of a great sleeping serpent that has crested the surface.
Immense Guardians. A popular myth is that in ancient times some sea serpents were magically bound to serve as guardians of secret isles and sunken treasures. A small number of foolhardy treasure hunters have sought the lairs of sea serpents, hoping to find riches. Few of these expeditions return, and even fewer come back with any treasures to show for it.
Credits
- Page One Art. Serpent of the Endless Sea by Kieran Yanner. Copyright Wizards of the Coast.
- Page Two Art. Lochmere Serpent by Sam Burley. Copyright Wizards of the Coast.
- This monster was created by u/aabrock with editing and feedback from u/ravenmaw, u/drudicdancing, u/lorien-of-loth and u/crashingcomp930.
They get bigger?
The monster represented here is a relatively small and
young sea serpent. If you wish to represent a larger
serpent just increase the CR of the creature to a
level appropriate to your party. For a truly elder sea
serpent, it may be more appropriate to treat the
creature as an environmental hazard rather than a
monster. Such creatures are the size of landmasses
and could even serve as the location for an adventure.
Sea Serpent
Gargantuan Monstrosity, unaligned
- Armor Class 18 (natural armor)
- Hit Points 217 (15d20+60)
- Speed 10 ft,. swim 50 ft.
STR DEX CON INT WIS CHA 25 (+7) 12 (+1) 18 (+4) 5 (-3) 12 (+1) 8 (-1)
- Saving Throws Dex +3, Cha +1
- Skills Perception +3, Stealth +3
- Damage Resistances bludgeoning, piercing, and slashing from nonmagical attacks
- Condition Immunities frightened, restrained
- Senses darkvison 120 ft, passive perception 13
- Languages —
- Challenge 13 (10,000 XP)
Legendary Resistance (2/Day). If the sea serpent fails a saving throw, it can choose to succeed instead.
Mirrored Scales. When the sea serpent is fully submerged in water it has advantage on stealth checks to remain hidden.
Siege Monster. The sea serpent deals double damage to objects and structures (already factored into its ensnare vessel ability).
Water Breathing The sea serpent can only breathe underwater.
Actions
Bite. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 23 (3d10+7) piercing damage. If the target is a creature, it is grappled (escape DC 17). Until this grapple ends, the target is restrained, and the sea serpent can't bite another target.
Swallow. The sea serpent makes one bite attack against a Large or smaller creature it is grappling. If the attack hits, that creature takes the bite's damage and is swallowed, and the grapple ends. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside the sea serpent, and it takes 21 (6d6) acid damage at the start of each of the sea serpent's turns.
If the sea serpent takes 30 damage or more on a single turn from a creature inside it, the sea serpent must succeed on a DC 15 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the sea serpent's head. If the sea serpent dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 20 feet of movement, exiting prone.Ensnare Vessel. The sea serpent targets a gargantuan or smaller ship. The ship's pilot must make a water vehicle check contested by the sea serpent's strength check. If the sea serpent succeeds the ship is grappled and may not move. Each round, at the beginning of the sea serpent's turn, a ship grappled in this way takes 36 (2d10+7, doubled for siege monster) bludgeoning damage as the sea serpent crushes it.
Once per round a person at the ship's helm may make a DC 17 water vehicles check. If the ship wins this check it is no longer grappled and may move normally.
Legendary Actions
The sea serpent can take 2 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.
Bite. The sea serpent makes one bite attack.
Bash. The sea serpent targets an adjacent 20 ft cube. Each creature in the area must make a DC 17 strength saving throw or take 12 (1d8+7) damage and either be knocked prone or pushed 10 feet in a direction of the sea serpent's choice as the serpent slams into them. A creature that succeeds on its saving throw takes half damage and suffers no other effect. All creatures experience the same secondary effect, either knocked prone or shoved in the same direction.
Swallow (Costs 2 Actions): The sea serpent uses its Swallow.
