Undine, Greater

Large elemental, neutral evil

Armor Class 15 (natural)
Hit Points 130 (20d10+40)
Speed 10 ft., Swim 60 ft.

19 (+4) 12 (+1) 14 (+2) 5 (-3) 8 (-1) 6 (-\1)

Skills Stealth +4
Damage Immunities lightning, thunder, any effect caused solely by air or gas
Condition Immunities cannot be affected by air or gas
Damage Resistances fire, Acid slashing, or piercing damage
Senses passive Perception 9
Languages Aquan
Challenge 7 (2,900 XP)


  • Camouflage. Water foul are able to blend in with almost any environment. They do so by lying still in the water. They can do this at any depth. When concealing themselves, they have advantage on stealth checks.
  • Shapeshifter. The water foul can assume any shape they have previously seen. They do this by manipulating the water around them. They cannot change their color except by pulling what is in the water into their form.


  • Slam. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8+4) bludgeoning damage. If the target is a creature of large size or smaller, it must succeed on a Strength save (DC 16) or be grappled. The creature can only have up to three targets grappled at a time.
  • Drown. If a creature ends its turn grappled by the undine, the undine begins to drown the target. The target is now considered restrained and begins to drown. If a creature is drowning, on the undine’s turn it automatically hits with its slam attack and does an additional 3d8 necrotic damage.
  • Trip. If a creature is standing in water and within 10 feet of the undine, the undine may, as a bonus action, attempt to trip the target. The target must make a Strength save (DC 16) or be knocked prone.


The water foul are evil fey that dwell entirely in water. In their true form, they are little more than light bluish, amoebic-like creatures that glide through water on thousands of invisible scintillas. They can become quite large and can be seen by the naked eye, but even then they appear as little more than a grease slick in the water or a bed of light bluish algae.

Plague of Water. Water foul are highly territorial creatures that dwell in all types of water. They are encountered in the deep oceans as well as lakes, ponds, rivers, creeks, wells, and birdbaths. The smaller the body of water the smaller the water foul. They defend their home against all intruders that are not natural to that water. Fish, alligators, sharks, whales, even aquatic elves would be left unmolested but all others would suffer an attack. Creatures who pass through or even come to drink at the water foul’s lair suffer a 50% chance of being attacked. The Water foul moves constantly like any predacious creature. Whether or not the creature has treasure depends upon its locale. If it is in a small pond or lake then anything it has slain will naturally sink or be drug to the bottom and left there. So treasure could possibly be found. If, however, the creature dwells in the ocean or a large lake or fast-moving river, then the chances of any treasure being found are negligible, as current and depth would have scattered it far and wide.

Shapeshifters. They are not very intelligent creatures, having little capacity to learn from their own experiences or think or communicate. They do, however, have an uncanny ability to remember shapes and to assume that shape in the future. A single encounter with a dog drinking at a water foul’s pond would allow the water foul to remember and take the shape of the dog in the future.

Native Elementals. Water foul are creatures natural to the material plane and are therefore not subject to being summoned or conjured. They are asexual and breed only during violent storms when water overflows its natural banks. During such moments the creatures instinctively split into two, one greater and one lesser. The lesser water foul immediately follows the natural flow of water seeking its own habitat within which to settle. They will follow runoff water into larger creeks and to ponds or wherever fortune should take them. If for whatever reason a water foul is stranded (its lake dries up, its runoff ends in sand, etc), they do not die, but become dormant, lying on the ground, waiting for the next rainfall. In such a state the water foul is not able to attack or defend itself and appears as little more than a snail’s track of slime on the ground. They can be captured in such a state and as a favorite pet of wizards and the like, they can go on the open market for 2000gp for a lesser to 10,000gp for a greater.

Section 15: Copyright Notice

5th Edition Monsters & Treasure of Airhde, 1st Printing, Copyright 2021, Troll Lord Games; Author Stephen Chenault & Jason Vey

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