D&D Monster Monday: Kelpie

D&D Monster Monday Kelpie

You gasp for air, but only water fills your lungs. The seaweed-like appendages of the kelpie coils around you even tighter. “I thought it was a person in distress, not a beast of the depths!” Foolish mortal, to the depths you go!

Have you ever had an adventure planned underwater, maybe in a shipwreck or a sunken cavern, that needed just a hint of seaweed monsters strangling the party to death in the depths of a murky loch? Yeah, I have too.

Thankfully, there’s a perfect creature for that situation. In fact, they’re purpose-built to lure in unsuspecting adventurers by disguising themselves as creatures or humanoids. Once their targets swim within their clutches, the kelpie will use their seaweed to constrict and drown them in the cold depths of the ocean.

Keep your head above water! Today, we’re trying to swim by the seaweed monstrosity, the kelpie, from Tales from the Yawning Portal.

Kelpie Lore

As far as I can tell the D&D team to their cues from the kelpie’s Scottish mythological origin. Its natural form seems to be like a cross between seaweed and a horse.

Kelpie are weird plant-like creatures that are natural inhabitants of murky waters. There’s not a ton of info in their official lore segment so there’s a lot left to the DM’s imagination.

The only concrete info in their lore blurb is that kelpies are known to morph their bodies to look like attractive humanoids from afar. They’ll use this form to lure unsuspecting people into their clutches beneath the water where the kelpie will grapple, kill, and presumably feast on their remains.

There’s no canon type of habitat that the kelpie seems to prefer so they could easily fit in an adventure in the depths of the ocean or at the bottom of a murky lake. They’re adaptable creatures and can be reflavored effortlessly thanks to their ability to change their form on a dime.

Kelpie Stats and Abilities

You can find the kelpie’s statblock on page 238 of Tales from the Yawning Portal.


Size: Medium plant
AC: 14 (Natural Armor)
Hit Points: 67 (9d8 + 27)
Speed: 10 ft., swim 30 ft.,
STR: 14 (+2)
DEX: 14 (+2)
CON: 16 (+3)
INT: 7 (-2)
WIS: 12 (+1)
CHA: 10 (+0)

This is a really weird array of ability scores. For one thing, Constitution is the kelpie’s highest ability score which is not something we see super often. Continuing with this weird trend, we have both Strength and Dexterity dead-even at a +2 modifier.

It’s fine to have both of these stats being +2 or higher, but it’s odd to have both of them as dead-even. One of these is clearly their primary attribute in terms of attack and damage rolls. It would’ve been nice for that frontrunner to be bumped to +3 so they’d have a bit more offensive power.

Their Charisma being a +0 modifier is also strange in my opinion. A core part of their lore and kit is their ability to shapeshift into a beautiful creature and charm their victims into their melee range. You’d think with that being said that they’d have at least a +1 to Charisma.

Their AC is alright, not impossible to hit but it’s an ok buffer. Same goes for their hit points. Thankfully they have some very solid resistances to bolster their defenses significantly.

Their movement speed clearly showcases their niche if you hadn’t figured it out already. They’re sluggish at best on land, but they can move damn quick in their natural habitat when they need to.

Resistances, Immunities, Saves, and Skills

Skills: Perception +3, Stealth +4
Damage Resistances: bludgeoning, fire, piercing
Condition Immunities: blinded, deafened, exhaustion
Senses: blindsight 60 ft., passive Perception 13
Languages: Common, Sylvan
Challenge: 4 (1,100 XP)

First thing’s first, our creature has some out-of-combat utility! Kelpies have two solid bonuses to Perception and Stealth checks, further enhancing their ability to be hidden guards or ambushers.

Their damage resistances are also really good. Many creatures have resistance to nonmagical bludgeoning and piercing, but kelpies have total resistance to both damage types. While they would gain fire resistance from fighting underwater regardless, it’s a nice resistance to have just in case your kelpie is fighting outside of their preferred location.

Condition immunities are always beneficial. The blinded and deafened immunities stem from the kelpie’s blindsight, but the immunity to exhaustion is a cool perk. They can use their 30 ft. of swim speed to chase after the party without ever tiring!

Blindsight is rad and it gives the kelpie quite a few perks in combat. They can sit in dark, murky water without worrying about needing to physically see their opponents. This sort of environment is perfect for a kelpie but adds on more challenges for the party.

In 3.5e D&D the kelpie’s creature type was fey. While this direct link isn’t in the kelpie’s 5e statblock or lore, the kelpie’s ability to speak Sylvan is a certainly nod to this.

Abilities and Traits

Amphibious.The kelpie can breathe air and water.

Seaweed Shape. The kelpie can use its action to reshape its body into the form of a humanoid or beast that is Small, Medium, or Large. Its statistics are otherwise unchanged. The disguise is convincing, unless the kelpie is in bright light or the viewer is within 30 feet of it, in which case the seams between the seaweed strands are visible. The kelpie returns to its true form if it takes a bonus action to do so or if it dies.

False Appearance. While the kelpie remains motionless in its true form, it is indistinguishable from normal seaweed.

Amphibious should come as no surprise to no one.

Seaweed Shape is part of the kelpie’s identity. This ability gives the kelpie a way to trick their prey into diving deep into the water, and honestly, it’s needed initially. The kelpie does not function well on land or really anywhere but underwater. Having a way to draw in their target is necessary. Once they’re within range, the kelpie can follow-up with Drowning Hypnosis and really cause some damage.

Kelpies also have False Appearance just like the gargoyle, meaning that they can be utilized as hidden guards for a specific location. The downside to a kelpie doing this compared to a gargoyle is that the kelpie must eat and sleep so they cannot sit there indefinitely. Regardless, it’s a fun tactic that their kit plays into.

Any way you slice it, the kelpie is the master of disguise beneath the waves. They fool passers-by into thinking they are a beautiful humanoid in distress or they can lay in wait outside of the entrance of an abandoned shipwreck ready to ambush their foe.


Multiattack. The kelpie makes two slam attacks.

Slam. Melee Weapon Attack: +4 to hit, reach 10 ft., one target. Hit: 11 (2d8 + 2) piercing damage. If the target is a Medium or smaller creature, it is grappled (escape DC 12).

Drowning Hypnosis. The kelpie chooses one humanoid it can see within 150 feet of it. If the target can see the kelpie, the target must succeed on a DC 11 Wisdom saving throw or be magically charmed while the kelpie maintains concentration, up to 10 minutes (as if concentrating on a spell).
The charmed target is incapacitated, and instead of holding breath underwater, it tries to breathe normally and immediately runs out of breath, unless it can breath water.
If the charmed target is more than 5 feet away from the kelpie, the target must move on its turn toward the kelpie 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 kelpie 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 kelpie’s hypnosis for the next 24 hours.

Slam is an excellent attack option. With Multiattack, a kelpie can deal 22 piercing damage per turn. Not only that, but they can grapple up to two Medium or smaller creatures per turn as well. The damage is alright, but the crowd control that comes with it is solid.

I feel like “chooses one humanoid it can see” is poor word choice for Drowning Hypnosis. I understand the intention, but kelpie don’t see they have blindsight. They use their other senses to perceive their environment.

With that being said, this is a very powerful ability and super-dangerous ability to use on an unsuspecting Player Character (PC). Failing the saving throw for Drowning Hypnosis is potentially a death sentence as it forces the target to expel all their held oxygen and breath in water. You’ll immediately begin drowning as you swim toward the kelpie. Even if you pass the saving throw on your subsequent attempt, you’re still out of oxygen.

You’ll probably combo it with either Seaweed Shape to entice a PC to swim towards the kelpie. They can only distinguish the kelpie’s true form if they are within 30 ft. They’re probably screwed by then considering that Drowning Hypnosis has a range of 150 ft.

Thankfully Drowning Hypnosis has a Wisdom saving throw DC of 11 to balance out the strong effects of the action. It’s easy enough to pass for a typical PC, but those that are unlucky enough to fail it will be in dire straits.

Kelpie Strengths

Hardy Defenses

14 AC and 67 HP are respectable base amounts for the kelpie’s survivability. Neither value is amazing, but they’re both average to slightly above-average. However, I would still argue that the kelpie has some excellent defenses and survivability potential.

For starters, they have resistances to three of the most common damage types in the game. They have resistance to ALL bludgeoning and piercing damage, not just damage from nonmagical weapons. That’s huge.

Their blindsight is an enormous boon and allows them to thrive in areas where an average PC will be at a serious disadvantage. This also comes with immunity to the blindness and deafness conditions.

Lastly, the kelpie’s False Appearance and Seaweed Shape traits give them the ability to lay in wait for ideal battlefield conditions. Having this type of battlefield control, along with their various forms of CC, ensures that the kelpie will be able to last as long as physically possible.

Kelpie art from DnD 3.5e
Oooh spooky, amphibious, seaweed horse! Credit: WotC.

Home Field Advantage

The kelpie is certainly a niche creature. They are meant to live on the floor of a large body of water, where they can entrap and drown their unsuspecting victims. Of course, the kelpie’s statblock gives them quite a few tools to thrive in this location.

For starters, they have poor base movement speed. However, when they’re swimming they are going to be damn quick. Underwater combat rules dictate that moving through water counts as difficult terrain unless you have swim speed. This effectively allows the kelpie to move at 2x the speed of an average PC. The party can’t easily escape.

Having 60 ft. of blindsight as their only type of sense is another excellent perk. Sure, they can’t physically see anything, but they can use their other senses to view the area around them perfectly.

How is this an advantage? You can drop a kelpie encounter in a murky lake where the PCs can’t see more than a few feet in front of them. However, the kelpie can function without skipping a beat. It’s difficult enough to fight underwater, but doing so when you can’t see is a nightmare.

Kelpie Weaknesses

One-Trick Pony

Their ability to thrive in deep, murky waters is both a blessing and a curse. The issue with a creature requiring a specific environment for optimal use is that if they’re ever taken outside of that environment they’re practically useless.

Drowning Hypnosis becomes considerably less dangerous when the target is not already submerged in water. If they can’t drown then it’s only a low-DC charm that lures the target toward the kelpie. There’s a high chance that the target will never be lured directly to the kelpie, it’s the drowning aspect of it that makes this action dangerous.

Honestly, a kelpie out of water is just a shitty roper.

This isn’t a challenging weakness to avoid when you’re designing an encounter with a kelpie in it. Keep the fight in water and don’t give your party a way to easily submerge or force the kelpie onto dry land.

You’ll probably get one or two good encounters out of a kelpie in a campaign because of their identity as a “one-trick pony”.

Susceptible to Magic and Ranged Attacks

The kelpie does have one glaring weakness. They don’t have really any answers to ranged attackers outside of their fire resistance (which they already would have from being underwater) and their Drowning Hypnosis.

However, if their target succeeds the DC 11 Wisdom save for Drowning Hypnosis then our kelpie is pretty screwed. They don’t have any ranged attacks to answer their attackers with.

While their superior swim speed will allow them to eventually catch up with the party’s ranged characters, the kelpie has a high chance of taking quite a bit of damage before making it there.

Also, their saving throw modifiers aren’t terrible, but not great either for a CR 4 creature (outside of Consitution). Sure, nothing is negative, but they don’t have anything outside of a +1 or +2 to avoid most spell saving throws that aren’t Consitution.

kelpie from DnD 1e's White Plume Mountain adventure
White Plume Mountain was the introduction of kelpies in D&D. Credit: WotC.

How to Play a Kelpie

Order Room Service

You work hard sitting at the bottom of the lake all day long. Why should you have to get up and make dinner when you can have it brought to you?

Use Seaweed Shape to turn yourself into something enticing for incoming adventurers or creatures. Once a sucker is bee-lining it to you, reel them in with Drowning Hypnosis and it’s off to the races!

Wait for the target to get as close as physically possible, then spring out with your 30 ft. of swim speed and attempt to grapple them with Slam. You get bonus points if they’re already in the process of drowning thanks to Drowning Hypnosis.

Once you have them in your clutches simply wait until they drown and voila! Dinner is served, and you barely had to move to get it.

Don’t Let Your Prey Escape!

One of the kelpie’s most glaring flaws is that if they’re taken out of their ideal battlefield/habitat, they immediately become noticeably weaker. What this means is that once your kelpie has identified their prey, they cannot let them leave the water under any circumstances.

As I mentioned earlier, kelpies are surprisingly well-equipped in the case of a chase encounter breaking out. They have swim speed which puts them well ahead of a typical PC in terms of speed. This means that there’s a great chance that the chase encounter will be over within a couple of rounds.

However, the kelpie is covered even if they cannot quickly end the chase encounter. Their immunity to the exhaustion condition ensures that they can continue to swim towards their targets at full-speed indefinitely. The party will have to be quick-thinking to escape these seaweed menaces.

Once the kelpies have caught up with the party their Slam attacks will be quite useful for dragging the party back down into the depths of the ocean.

5 Kelpie Plot Hooks

  1. The Forgotten Grotto – Underwater ruins proclaimed to have riches beyond your wildest dreams attract many a treasure hunter. It’s odd though how none who seek out the treasure seem to return.
  2. Symbiotic Relationship – A tribe of merrow leave their den to hunt during the day. The kelpie, disguised as seaweed ensure that their lair is protected. The merrow give the kelpies some of their supplies and provide them with shelter as payment.
  3. A Curious Specemin – A bontanist recieved a unique type of seaweed. They’d like for you to travel to the location this specemine was found and procure them some additional samples.
  4. The Haunted Swimming Hole – It’s summer time and the livin’ is easy. Well, unless you’ve visited the local lake for a swim, because chances are, you have mysteriously disappeared!
  5. Invasive Species – Someone dumped kelpies into a nearby lake and they’re eating all the fish! Get rid of them before the ecosystem is ruined!


The kelpie is a fun creature with unique abilities. They have a variety of options as to how they’d like to strangle or drown their enemies to death at the bottom of a murky body of water.

Their only flaw is that they have a specific niche in which they need to be played. Putting a kelpie somewhere other than a deep body of water will yield you poor results. You also need to know just when to strike your opponent or else the fight can go sour quickly.

While they do have some aspects of high-risk, high-reward play they have enough consistent damage, maneuverability, and survivability that even if the whole party passes the DC 11 saving throw against being charmed, your kelpies will still put up one hell of a memorable fight.

If your table is angling for an underwater exploration game, the kelpie should definitely be featured.

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