Huge fiend (phlegethite), chaotic evil

Armor Class 16 (natural armor)
Hit points 184 (16d12 + 80)
Speed 0 ft., swim 60 ft.

20 (+5) 12 (+1) 20 (+5) 7 (-2) 14 (+2) 10 (+0)

Skills Intimidation +6, Perception +8, Performance +6, Stealth +7
Saving Throws Str +11, Con +11
Damage Resistances radiant
Damage Immunities cold, fire
Condition Immunities charmed
Senses darkvision 120 ft., tremorsense 30 ft., passive Perception 13
Languages Infernal
Proficiency Bonus +6
Challenge 17 (18,000 XP)


  • Boiling Aura. At the start of each of the marool’s turns, each creature within 10 feet of it takes 10 (3d6) fire damage. A creature that touches the marool or hits it with a melee attack while within 5 feet of it takes 10 (3d6) fire damage. Being underwater doesn’t grant resistance against this damage. Multiple Eyes The marool has advantage on saving throws against being blinded and can’t be surprised while it isn’t incapacitated.
  • Variable Illumination. The marool sheds bright light in a 5 to 20-foot radius and dim light for an additional number of ft. equal to the chosen radius. The marool can alter the radius as a bonus action.
  • Water Breathing. The marool can breathe only underwater.


  • Bite. Melee Weapon Attack: +6 to hit, reach 15 ft., one target. Hit: 16 (2d10 + 5) piercing damage plus 10 (3d6) fire damage.
  • Luring Light. The marool chooses one creature it can see within 150 feet of it. If the target can see the marool, the target must succeed on a DC 16 Wisdom saving throw or be magically charmed while the marool maintains concentration, up to 10 minutes (as if concentrating on a spell). The charmed target is incapacitated, and instead of holding its breath underwater, it tries to breathe normally and immediately runs out of breath, unless it can breathe water. If the charmed target is more than 5 feet away from the marool, the target must move on its turn toward the marool by the most direct route, trying to get within 5 feet. It doesn’t avoid opportunity attacks. Before moving into damaging terrain, such as lava or a pit, and whenever it takes damage from a source other than the marool or drowning, the target can repeat the saving throw. A charmed target can also repeat the saving throw at the end of each of its turns. If the saving throw is successful, the effect ends on it. A target that successfully saves is immune to this marool’s Glowing Lure for the next 24 hours.
  • Shipwreck Rays. The marool shoots three rays, choosing one of the three targets it can see within 120 feet of it. If the target is a creature, it must succeed on a DC 16 Dexterity saving throw or take 45 (10d8) force damage. If the target is a Large or smaller nonmagical object, it is disintegrated without a saving throw. If the target is a Huge or larger object or creation of magical force, this ray disintegrates a 10-foot cube of it. Exultant Song (Recharged 5-6). The creature sings a song in Infernal of impending doom. Creatures within 600 feet of the marool that can hear its song must succeed on a DC 16 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 marool’s Exultant Song for the next 24 hours.


The marool is a massive creature resembling a monstrous anglerfish, yet it has a unique array of features. It breaches the surface of the water with its whale-sized body, covered in dozens of luminous eyes that emit a dim light. Its head is adorned with feelers and tentacles.

The marool is a predator of the lightless ocean depths, equipped with luminous eyes and sensory appendages to detect vibrations in water or air. It dwells primarily on the ocean floor but surfaces, especially on moonless nights. With a malevolent and dim intelligence, marools revel in destroying ships and consuming sailors.

Marools employ mesmerizing lights to lure multiple victims into position, and then swiftly dispatch them with their bite. They delight in music and croon with disturbing lyrics that can be heard for miles, especially by those who understand Infernal.

Marools are native to the Pyriphlegethos on the Seventh Circle of Infernus. They bring the burning nature of that river with them into the Prime Plane, and revel in the destruction they can bring to anyone they can catch.

Section 15: Copyright Notice

5E RPG: Celtic Bestiary. Copyright 2023, Mal and Tal Enterprises, LLC; Author Michael Tresca.

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