Family: Aquatic & Fish

Huge beast, unaligned

Armor Class 14 (natural armor)
Hit Points 253 (22d10+132)
Speed 0 ft., swim 50 ft.

20 (+5) 12 (+1) 23 (+6) 3 (-4) 12 (+1) 7 (-2)

Skills Perception +5
Senses blindsight 120 ft., passive Perception 13
Challenge 12 (8,400 XP)

Special Traits

  • Swim-By Attack. A dinichthys is perfectly suited for attacking on the move. A dinichthys that uses its action to attack does not provoke opportunity attacks for the rest of its turn.
  • Vicious Bite. The dinichthys scores critical hits on natural rolls of 15 to 20. In addition, its critical hit damage is always maximised doing 35 piercing damage and inflicting an additional 7 (2d6) necrotic damage from bleeding. This bleeding can only be stopped with a DC 15 Wisdom (Medicine) check or through any magical healing. This damage is cumulative. For example, a creature who has been hit by two critical hits from a dinichthys vicious bite suffers 14 (4d6) necrotic damage per round.
  • Water Breathing. The dinichthys can breathe only underwater.


  • Multiattack. The dinichthys makes two bite attacks.
  • Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 22 (5d6 + 5) piercing damage.


This horrific fish has a powerful grey body, with a head of hard white plates. Its wide mouth more resembles curved blades of bloodstained bone.

Primordial punisher. Among the deadlier animals of the sea, the mighty dinichthys holds its own against dragons and magical beasts. Its punishing bite allows it to both defend itself and feed from the sea’s hardiest animals. Dinichthyses hunt at any depth greater than 20 feet, chasing prey for miles in any direction before resuming a natural migration toward decennial mating waters.

Neverfull. Dinichthyses are voracious, often biting a chunk of flesh out of a sizable creature so it can follow the bleeding quarry to any social unit it might flee to for protection.

Dinichthyses live for approximately 100 years. An adult is 30 feet long and weighs 22,000 pounds.

Section 15: Copyright Notice

Sea Monsters (5E) © 2021, Legendary Games; Authors Michael Ritter, Michael “solomani” Mifsud, Robert J. Grady, Mark Hart, Jeff Ibach, Alex Riggs, Scott D. Young, Jeff Lee, Matt Kimmel, and Jason Nelson.

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