Sea Serpent
Huge or Gargantuan • Beast • Unaligned
Armor Class 18
Hit Points 147 (14d12 + 56)
Speed 15 ft., swim 60 ft.
Initiative +2 (12)
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 21 (+5) | 15 (+2) | 19 (+4) | 3 (-4) | 14 (+2) | 5 (-3) |
Saving Throws Str +9, Con +8
Skills Perception +6, Stealth +6
Damage Immunities cold
Senses blindsight 30 ft., passive Perception 16
Languages —
CR 9 (XP 5,000; PB +4)
Blood Frenzy. The serpent has advantage on attack rolls against any creature that doesn’t have all its hit points.
Water Breathing. The serpent can breathe only underwater.
ACTIONS
Multiattack. The serpent one Bite attack and uses its Constrict. If Screech is available to use, the serpent can replace its Bite attack with it.
Bite. Melee Weapon Attack: +9, reach 15 ft. Hit: 24 (3d12 + 5) piercing damage plus 10 (3d6) cold damage.
Constrict. Strength Saving Throw: DC 17, one Large or smaller creature the serpent can see within 5 feet. Failure: 18 (3d8 + 5) bludgeoning damage, the target is grappled (escape DC 17), and it is restrained until the grapple ends.
Screech (Recharge 5-6). Constitution Saving Throw: DC 16, each creature that is not deafened in a 90-foot emanation originating from the serpent. Failure: 10 (3d6) thunder damage and the target is stunned until the end of its next turn. Success: Half damage.
Sea Serpent
Huge or Gargantuan • Beast • Unaligned
Armor Class 17
Hit Points 114 (12d12 + 36)
Speed 15 ft., swim 60 ft.
Initiative +1 (11)
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 19 (+4) | 13 (+1) | 17 (+3) | 3 (-4) | 12 (+1) | 5 (-3) |
Saving Throws Str +7, Con +6
Skills Perception +4, Stealth +4
Damage Immunities cold
Senses blindsight 30 ft., passive Perception 14
Languages —
CR 6 (XP 2,300; PB +3)
Blood Frenzy. The serpent has advantage on attack rolls against any creature that doesn’t have all its hit points.
Water Breathing. The serpent can breathe only underwater.
ACTIONS
Multiattack. The serpent one Bite attack and uses its Constrict. If Screech is available to use, the serpent can replace its Bite attack with it.
Bite. Melee Weapon Attack: +7, reach 15 ft. Hit: 17 (2d12 + 4) piercing damage plus 7 (2d6) cold damage.
Constrict. Strength Saving Throw: DC 15, one Large or smaller creature the serpent can see within 5 feet. Failure: 13 (2d8 + 4) bludgeoning damage, the target is grappled (escape DC 15), and it is restrained until the grapple ends.
Screech (Recharge 5-6). Constitution Saving Throw: DC 14, each creature that is not deafened in a 90-foot emanation originating from the serpent. Failure: 7 (2d6) thunder damage and the target is stunned until the end of its next turn. Success: Half damage.
Sea Serpent
Huge or Gargantuan • Beast • Unaligned
Armor Class 19
Hit Points 184 (16d12 + 80)
Speed 15 ft., swim 60 ft.
Initiative +3 (13)
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 23 (+6) | 17 (+3) | 21 (+5) | 3 (–4) | 15 (+2) | 5 (–3) |
Saving Throws Str +10, Con +9
Skills Perception +6, Stealth +7
Damage Immunities cold
Senses blindsight 30 ft., passive Perception 16
Languages —
CR 12 (XP 8,400; PB +4)
Blood Frenzy. The serpent has advantage on attack rolls against any creature that doesn’t have all its hit points.
Water Breathing. The serpent can breathe only underwater.
ACTIONS
Multiattack. The serpent one Bite attack and uses its Constrict. If Screech is available to use, the serpent can replace its Bite attack with it.
Bite. Melee Weapon Attack: +10, reach 15 ft. Hit: 32 (4d12 + 6) piercing damage plus 14 (4d6) cold damage.
Constrict. Strength Saving Throw: DC 18, one Large or smaller creature the serpent can see within 5 feet. Failure: 24 (4d8 + 6) bludgeoning damage, the target is grappled (escape DC 18), and it is restrained until the grapple ends.
Screech (Recharge 5-6). Constitution Saving Throw: DC 17, each creature that is not deafened in a 90-foot emanation originating from the serpent. Failure: 14 (4d6) thunder damage and the target is stunned until the end of its next turn. Success: Half damage.
QUICK REFERENCE
Habitat
- Dwells in deep oceans, high seas, and sunken trenches
- Sometimes lairs in flooded caves, shipwreck graveyards, or whirlpools.
- Elemental plane of water
Behavior
- A relentless yet simple-minded apex predator, striking ships from below with terrifying force and picking off crew from the deck
- Drawn to blood in the water even when it is miles away
- Hunts alone or in pairs when it is mating season
Information (Intelligence Check)
- DC 12 Nature: Recognize it as a rare but natural predator of the seas, can grow to enormous sizes (Huge to even sometimes Gargantuan)
- DC 16 Animal Handling: Knows that its screech can stun entire crews, leaving ships helpless
- DC 20 Survival: Realize that it strikes wounded prey first and only retreats when its tummy is filled or it is critically wounded
Combat
- Will attack and sink small ships from the bottom if possible, otherwise attacks crew directly
- Opens with Screech to stun foes, leaving them helpless, especially when thrown into the water
- Attacks are straightforward: attack what bleeds or hurts it most
- When wounded, it changes to guerrilla tactics, uses its reach, and then submerges into the water or focuses targets that are thrown overboard, which it will try to drag underwater with Constrict and hold them until they drown
Loot Ideas
- Serpent scales or fangs and bones, which can be crafted into equipment
- Meat, which is a rare delicacy
- Undigested treasures or former prey
USING MONSTER VARIANTS
Monster variants allow the GM to adjust encounters to better match the party’s strength, narrative needs, or world-building logic. A weaker variant may represent a juvenile, wounded, or lesser specimen, while a stronger variant can serve as a leader, champion, ancient creature, or apex predator.
Variants can be used to fine-tune difficulty without changing the core identity of the monster, making them ideal for scaling encounters, reinforcing hierarchy within a faction, or creating memorable boss-style enemies. You can even use the same stat block but different variants in the same encounter if you want.
Design Note. Each monster is primarily balanced around its normal version. Weaker and stronger variants are derived adjustments and may not always preserve every tactical nuance or “feel” of the original creature. GMs are encouraged to review variants carefully and adjust abilities or tactics as needed to best suit their table.