Dragon, Ketos

Gargantuan dragon, chaotic evil

Armor Class 22 (natural armor)
Hit Points 367 (21d20 + 147)
Speed 40 ft., swim 40 ft.

27 (+8) 14 (+2) 25 (+7) 8 (-1) 15 (+2) 14 (+2)

Saving Throws Dexterity+7, Constitution+12, Wisdom+7, Charisma+7
Damage Immunities thunder
Damage Resistances bludgeoning, piercing, and slashing from nonmagical attacks
Condition Immunities prone
Skills Perception +7, Stealth +7
Senses darkvision 120 ft., passive Perception 17
Languages Draconic
Challenge 24 (62,000 XP)

Special Traits

  • Amphibious. The dragon can breathe air and water.
  • Legendary Resistances (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.


  • Multiattack. The dragon can use its Frightful Presence. It then makes two attacks: one with its bite and one to constrict.
  • Bite. Melee Weapon Attack: +13 to hit, reach 15 ft., one target. Hit: 19 (2d10 + 8) piercing damage.
  • Constrict. Melee Weapon Attack: +13 to hit, reach 20 ft., one Large or smaller creature. Hit: 19 (2d10 + 8) bludgeoning damage. The target is grappled (escape DC 21) if the ketos dragon isn’t already constricting a creature, and the target is restrained until this grapple ends.
  • Thunder Breath (Recharge 5-6). The dragon exhales acid in a 90-foot cone. Each creature in that cone must make a DC 20 Constitution saving throw, taking 67 (15d8) thunder damage on a failed save, or half as much damage on a successful one.
  • Frightful Presence. Each creature of the dragon’s choice that is within 120 feet of the dragon and aware of it must succeed on a DC 15 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 dragon’s Frightful Presence for the next 24 hours.
  • Swallow. The ketos dragon makes one bite attack against a Medium or smaller target it is grappling. If the attack hits, the target is also swallowed, and the grapple ends. While swallowed, the target is blinded and restrained, it has total cover against attacks and other effects outside the ketos dragon, and it takes 21 (6d6) acid damage at the start of each of the ketos dragon’s turns. An ketos dragon can have only one creature swallowed at a time. If the ketos dragon takes 30 damage or more on a single turn from the swallowed creature, the ketos dragon must succeed on a DC 20 Constitution saving throw at the end of that turn or regurgitate the creature, which falls prone in a space within 10 feet of the ketos dragon. If the ketos dragon dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 15 feet of movement, exiting prone.
  • Tail. Melee Weapon Attack: +13 to hit, reach 20 ft., one target. Hit: 17 (2d8 + 8) bludgeoning damage.

Legendary Actions

The ketos dragon can take 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 ketos dragon regains spent legendary actions at the start of its turn.

  • Detect. The dragon makes a Wisdom (Perception) check.
  • Tail Attack. The dragon makes a tail attack.
  • Chomp (Costs 2 Actions). The ketos dragon makes one bite attack or uses its Swallow.


This sea serpent is entirely aquatic, with hundreds of fins dispersed amongst its coils ending in a fish-like tail. Its eyes flicker brightly when roused and its roar is like thunder.

Ketos dragons enjoy snatching morsels from coasts and off ships. For this reason, ketos dragons are often given sacrifices.

Section 15: Copyright Notice

5E RPG: Ancient Adventures. Copyright 2020, Mal and Tal, LLC; Author Michael Tresca.