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Sea Serpent, Deep Hunter

Gargantuan dragon, lawful neutral

Armor Class 19 (natural armor)
Hit Points 385 (22d20 + 154)
Speed 0 ft., swim 80 ft.

26 (+8) 14 (+2) 25 (+7) 7 (–2) 13 (+1) 14 (+2)

Saving Throws Strength +15, Dexterity +10, Constitution +14
Skills Athletics +15, Perception +8
Damage Immunities poison
Condition Immunities poisoned, prone
Senses darkvision 60 ft., passive Perception 18
Languages Aquan, Draconic
Challenge 21 (33,000 XP)

Special Traits

  • Amphibious. The deep hunter serpent can breathe air and water.
  • Siege Monster. The deep hunter serpent deals double damage to objects and structures.


  • Multiattack. A deep hunter serpent attacks once with its tail and either bites or uses its swallow attack.
  • Bite. Melee Weapon Attack: +15 to hit, reach 10 ft., one target. Hit: 34 (4d12 + 8) piercing damage plus 22 (4d10) poison damage, and the target is grappled (escape DC 23) and restrained. The deep sea hunter can’t make a bit attack while it has a creature grappled with its bite.
  • Tail Slap. Melee Weapon Attack: +15 to hit, reach 20 ft., one target. Hit: 30 (4d10 + 8) bludgeoning damage and the target is pushed 15 feet away and knocked prone.
  • Swallow. A Large or smaller target grappled by the serpent’s bite attack 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 deep hunter serpent, and it takes 42 (12d6) acid damage at the start of each of the deep hunter serpent’s turns. If the deep hunter takes 30 damage or more on a single turn from a creature inside it, the serpent must succeed on a DC 25 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 serpent. If the serpent dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 15 feet of movement, exiting prone.

Legendary Actions

The deep hunter sea serpent can take up to 3 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. The serpent regains spent legendary actions at the start of its turn.

  • Golden Bliss (Inhaled). A creature subjected to this poison must succeed on a DC 13 Constitution saving throw or be poisoned for 1 minute. While poisoned, the target is stunned and has advantage on Intelligence, Wisdom, and Charisma saving throws against spells and magical effects. The poisoned target can repeat the saving throw at the end of each of its turns, ending the effect on a success.
  • Tail Attack. The deep hunter serpent uses its Tail Slap.
  • Coiling Maneuver (Costs 2 Actions). The deep hunter sea serpent attempts to grapple a Huge or smaller target. The target must make a DC 23 Strength saving throw or be grappled and restrained. The sea serpent can’t use its other legendary actions or its Tail Slap if it’s grappling a target. At the beginning of each of the brine serpent’s turns, the grappled target takes 30 (4d10 + 8) bludgeoning damage.
  • Unhinge Jaw (Costs 3 Actions). The deep hunter uses its bite attack on all creatures of Large size or smaller in a 10-foot cube within 15 feet of the deep hunter. If the attack hits on any of the creatures, it can use its swallow ability.


This serpent is about 60 feet long and 10 feet thick. Its body scales are smooth, each about the size of a large shield, and the entire serpent is deep green to jet black in color, with eyes a solid, nearly black red color.

The immense deep hunter serpent lives in deep oceans and delights in hunting down and killing the most fearsome creatures of the sea. The deep hunter lives on the ocean floor, usually near thermal vents and volcanic areas where it is relatively warm. However, when hunting it may be encountered just about anywhere at sea; its preferred prey are krakens and the largest whales, though it may attack any other fearsome sea predator — the more dangerous, the better.

The deep hunter sea serpent is seldom seen near the surface, as its prey tends to stick to deep waters. It does not initiate combat against creatures it sees as its inferiors, but if it does regard a creature as a threat, it uses stealth to surprise its prey when possible and launches into a full-scale assault using all of its physical attacks to the best of its ability.

Section 15: Copyright Notice

Tome of Horrors © 2018, Frog God Games, LLC; Authors: Kevin Baase, Erica Balsley, John “Pexx” Barnhouse, Christopher Bishop, Casey Christofferson, Jim Collura, Andrea Costantini, Jayson ‘Rocky’ Gardner, Zach Glazar, Meghan Greene, Scott Greene, Lance Hawvermale, Travis Hawvermale, Ian S. Johnston, Bill Kenower, Patrick Lawinger, Rhiannon Louve, Ian McGarty, Edwin Nagy, James Patterson, Nathan Paul, Patrick N. Pilgrim, Clark Peterson, Anthony Pryor, Greg Ragland, Robert Schwalb, G. Scott Swift, Greg A. Vaughan, and Bill Webb