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Demon, Hydrodemon

Large fiend (demon), neutral evil

Armor Class 15 (natural armor)
Hit Points 85 (9d10 + 36)
Speed 30 ft., fly 40 ft., swim 60 ft.

18 (+4) 14 (+2) 18 (+4) 8 (-1) 11 (+0) 14 (+2)

Saving Throws Dexterity +5, Constitution +7
Skills Perception +6
Damage Resistances cold, fire, lightning
Damage Immunities poison
Condition Immunities poisoned
Senses darkvision 60 ft., passive Perception 16
Languages Abyssal
Challenge 5 (1,800 XP)

Special Traits

  • Amphibious. The hydrodemon can breathe air and water.
  • Magic Resistance. The hydrodemon has advantage on saving throws against spells and other magical effects.
  • Magic Weapons. The hydrodemon’s weapon attacks are magical.
  • Innate Spellcasting. The hydrodemon’s spellcasting ability is Charisma (spell save DC 13, +5 to hit with spell attacks). It can innately cast the following spells, requiring no material components:


  • Multiattack. The hydrodemon makes three attacks: one with its bite and two with its claws. The demon can use its Sleep Spittle instead of using its bite.
  • Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) piercing damage, and the target is grappled (escape DC 14). Until this grapple ends, the target is restrained and the demon can’t bite another target.
  • Claws. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 11 (2d6 + 4) slashing damage.
  • Sleep Spittle. One target within 60 ft. must succeed on a DC 15 Wisdom saving throw or fall unconscious for 1 minute. The sleeping target can be awakened if someone uses an action to shake or slap the sleeper awake, and the target will wake if it takes damage.
  • Summon (1/day). The demon chooses what to summon and attempts a magical summoning. A hydrodemon has a 30% chance of summoning one hydrodemon. A summoned demon appears in an unoccupied space within 60 feet of its summoner, acts as an ally of its summoner, and can’t summon other demons. It remains for 1 minute, until it or its summoner dies, or until its summoner dismisses it as an action.


This massive frog-like creature stands nearly 10 feet tall. Its flesh is warty and dark green and its eyes are sickly yellow. It has large flaps of skin under its arms that seemingly function as wings.

Hydrodemons are frog-like demons that swim the River Styx. They are the only known creatures in existence that can touch the waters of the Styx without suffering any ill effects.

Hydrodemons are 10 feet tall and weigh about 4,000 pounds. They move by leaping in a manner akin to a frog. Large flaps of skin under their arms allow them seemingly to glide when leaping. The flesh of a hydrodemon is warty and green. Its eyes are a sickly yellow in color.

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