Fathomless Warlock in D&D 5e | Full Subclass Guide (2023)

Lurking in the darkest depths of the oceans dwells a powerful entity that might be willing to strike a deal.

In service to such entities, Fathomless Warlocks call upon the power of what lies beneath the waves to crush their enemies. How’s that for 20,000 leagues of terror?!

Channel the might of the sea with this full guide to the Fathomless Warlock in D&D 5e!

What is the Fathomless Warlock in D&D 5e?

A Fathomless Warlock has entered into a pact with some powerful aquatic entity. This could be a Kraken, something from the Elemental Plane of Water, or some other force entirely.

Whatever the nature of your patron, you are now able to harness a fraction of their power to aid you on your journey.

Tentacles you summon can be used to lay the smackdown on enemies while also protecting yourself and your party. Your expanded spell list harnesses all the power of the sea to give you more casting options for both damage and utility purposes.

As you expand your Patron’s knowledge about the world above the waves, you’re a bona fide force of nature!

The Fathomless Warlock is one of two Patron options released in Tasha’s Cauldron of Everything.

Role in the Party

As a Fathomless Warlock, you’re a combat caster who is also able to control the battlefield.

Your spells and abilities deal some very solid damage, but the tentacle you can summon with your Tentacle of the Deeps feature is going to be your best friend.

Whether you’ve got the tentacle summoned or not, you’re more than capable of shining in combat!

Some of your features provide some extra utility for yourself and the party. These features’ usefulness is mostly determined by what kind of campaign you’re playing since they’re water-based, but they’re far from bad!

Related: The Complete Guide to the Warlock Class in D&D 5e!

Fathomless Warlock Features 5e

So let’s dive right into the deep end and see what kind of abilities the Fathomless Patron is offering you!

Expanded Spell List (Level 1)

Let’s start at the beginning with the spells that you gain for choosing the Fathomless as your patron.

Spell Level	Spells
1	Create/Destroy Water, Thunderwave
2	Gust of Wind, Silence
3	Lightning Bolt, Sleet Storm
4	Control Water, Summon Elemental (Water Only)
5	Cone of Cold, Bigby’s Hand (appears as a tentacle)

All in all, this isn’t a bad spell list. It’s pretty well balanced and fits the theme of the class without making you useless out of water.

Create/Destroy Water is pretty situational. As a Warlock, your spell slots are very limited so I’m not sure how much mileage you’ll really get out of it. Thunderwave does make for a solid defensive spell though. If you find yourself getting swarmed, you can send the baddies flying!

Your level 2 spells are solid for helping you control the battlefield. Gust of Wind forces enemies to only have half as much movement speed if they’re trying to get to you while Silence completely shuts down casters.

Lightning Bolt and Sleet Storm are both useful options as level 3 spells. Lightning Bolt can ruin the day of any enemies who happen to be standing in a straight line while Sleet Storm is a potent control spell.

For your level 4 spells, it can either be awesome or pretty “meh.” If you’re playing a naval campaign or are at least near water, Control Water can be crazy powerful. Otherwise, it’s largely forgettable. Being able to summon Water Elementals is cool, though. Their Whelm ability can be merciless if the target can’t make its saves!

Finally, your level 5 spells are both incredibly powerful options. Cone of Cold covers a large area and deals some respectable damage if you can line your enemies up just right. Bigby’s Hand (or, rather, Bigby’s Tentacle in this case…) is an infinitely useful spell that can be used for damage, support, or utility all wonderfully!

Tentacle of the Deeps (Level 1)

Right from level 1, you’ve got your primary feature from the Fathomless patron.

Knock, knock!

Who’s there?

TENTACLE!

As a bonus action, you summon a 10-foot long tentacle at a point you can see within 60 feet of you. This tentacle lasts for 1 minute or until you use this feature to create another tentacle.

When you create the tentacle, you can make a melee spell attack against one creature within 10 feet of it. On a hit, the target takes 1d8 cold damage and its speed is reduced by 10 feet until the start of your next turn. When you reach level 10 in this class, the damage increases to 2d8.

As a bonus action on your turn, you can move the tentacle up to 30 feet and repeat the attack.

Ok, so this is impressive and gives you some reliable damage output every turn with your bonus action. Not only is your enemy taking damage, but you’re reducing their speed quite a bit.

Being able to summon this tentacle from 60 feet away opens up quite a bit of tactical options for you.

Look for where it can be the most disruptive to your enemies and let it go wild! This is especially useful for dealing with spellcasters who will frequently be squishier and in the enemy’s backline!

Depending on how you’ve built your Warlock, this ability can perfectly work with your action economy. It’s bonus action-heavy, so you’ll want to make sure you’ve got the bonus actions to spare!

Just keep in mind that you can only use this a number of times per day equal to your proficiency bonus. Unlike your spells, you’ll need to take a long rest to regain any uses of Tentacle of the Deeps.

Gift of the Sea (Level 1)

Your final level 1 feature, Gift of the Sea, is pretty straightforward.

You can now breathe underwater and you have a swimming speed of 40 feet.

This is one of those features that I was talking about earlier. Depending on what type of campaign you’re playing, this could be either high-impact or basically forgettable.

Abilities like this are why having a Session Zero is so important! If the game mostly takes place in the desert, being able to swim fast and breathe underwater isn’t exactly helpful.

If there are parts of your game that involve swimming, however, you’re now the ideal choice!

It’s probably not a bad idea to read up on how Underwater Combat works in that case though!

Oceanic Soul (Level 6)

Your next power-up as a Fathomless Warlock comes at level 6 with two new abilities. The first of these is the Oceanic Soul feature.

You gain resistance to cold damage. When you are fully submerged, any creature that is also fully submerged can understand your speech and you can understand theirs.

Having cold resistance is pretty helpful since cold damage isn’t necessarily uncommon. Adventures that take place underwater or in arctic environments like Icewind Dale: Rime of the Frostmaiden will be where this resistance really shines.

The second part of this feature lets you effortlessly communicate with any creature as long as you’re both underwater.

I think the spirit of this ability is mostly that you can now naturally talk to all kinds of aquatic creatures with ease. But it isn’t limited to just your fishy friends!

You can use it to deal with language barriers with other creatures, but you’ll want to find a way to communicate what you’re doing. While you’re just trying to have a conversation, your new friend might interpret things differently if you start trying to hold them underwater!

Guardian Coil (Level 6)

Your second feature at level 6 is Guardian Coil. This feature gives your Tentacle of the Deeps a convenient defensive ability.

When you or a creature you can see takes damage while within 10 feet of the tentacle, you can use your reaction to choose one of those creatures and reduce the damage to that creature by 1d8. When you reach level 10 in this class, the damage reduced by the big tentacle increases to 2d8.

For most Warlocks, you don’t really get too many uses for your reactions. That means that you can pretty easily use your Guardian Coil feature every round without conflicting with your other abilities.

You will already want your Tentacle of the Deeps within smacking distance of your enemies. Having it near your allies as well lets you provide some extra defense for them with your reaction while you use your bonus action to attack with the tentacle.

Guardian Coil is pure value for the Fathomless Warlock!

Grasping Tentacles (Level 10)

The Grasping Tentacles feature you get from level 10 gets you a free spell that helps control the battlefield and gives you a defensive buff.

You learn the spell Evard’s Black Tentacles. It counts as a Warlock spell for you, but it doesn’t count against the number of spells you know. You can cast it once without a spell slot and you regain the ability to do so when you finish a long rest.

When you cast this spell, your patron’s magic grants you a number of temporary hit points equal to your Warlock level.

Damage can’t break your concentration on this spell.

With this feature, you’re able to cast Evard’s Black Tentacles once per long rest for free.

The spell makes large tentacles fill a 20-foot square. The space is now difficult terrain and creatures who enter the area for the first time or start their turn there need to make a Dexterity saving throw or take 3d6 bludgeoning damage and be restrained.

A creature that’s already restrained takes 3d6 bludgeoning damage. To escape, the creature has to make its choice of a Strength or Dexterity check (not a save!) vs your spell save DC.

On its own, this is a gnarly spell for controlling a sizeable chunk of the battlefield. Getting to cast it for free makes it even better!

But the Fathomless Warlock Patron has your back and adds in some extra spice.

You’ll gain extra temporary hit points based on your Warlock level which will help you absorb some damage.

Worried about losing concentration if you get hit? Worry no more! Damage won’t make you lose concentration on this spell (though the other concentration rules still apply!)

Fathomless Plunge (Level 14)

The Fathomless Warlock’s final ability is a teleporting ability that can help you and your allies instantly teleport up to a mile away.

As an action, you can teleport yourself and up to five other willing creatures that you can see within 30 feet of you. Amid a whirl of tentacles, you all vanish and reappear up to 1 mile away in a body of water you’ve seen (pond size or larger) or within 30 feet of it. Each of you appear in an unoccupied space within 30 feet of the others.

Once you use this feature, you can’t use it again until you finish a short or long rest.

As far as teleportation abilities go, a mile is pretty great.

Just be sure that you’re taking notes of the bodies of water around you. You need something that is at least the size of a pond for this ability to work. As funny as it would be to magically emerge from a random mop bucket, you need plenty of water and space for this feature.

Sometimes you just need or want a quick escape. That’s where this ability really comes in handy.

Maybe the party found themselves over their heads in combat or the dice have just decided to be difficult. If there’s a body of water within a mile of you, you can make a quick escape to lick your wounds and try again later.

Work with your party’s Druid or Ranger to mark down where you can teleport to on the map. Their abilities make them great for scouting and they can help you figure out your teleportation options.

If you can keep track of your teleportation options, this is a nifty ability to have up your sleeve!

Pact Boons for Fathomless Warlocks in D&D 5e

So now that we’ve covered the features you gain from the Fathomless Warlock Patron, let’s look at your Pact Boon options.

Ultimately, you can choose whatever you’d like. This is more of my general opinion on each Pact Boon as it relates to the Fathomless Warlock.

For more information about each of these pacts, you can also check out my full guide to the Warlock’s Pact Boons!

Pact of the Blade

When I first read the Fathomless Warlock’s information, I had mental images of a character being able to summon weapons with a splash of seawater.

However, I don’t think this Pact Boon really plays to the strengths of the Fathomless Warlock specifically. It’s a great Pact Boon for any Warlock, but you don’t really gain any particularly useful synergies in this case.

The Fathomless Warlock really lends itself towards heavy casting with damage output and battlefield control.

There’s potential for something interesting here (especially when your Tentacle of the Deep is also on the field), but I think there are better options mechanically.

Pact of the Chain

If you take the Pact of the Chain, having a familiar can really increase the utility that you offer the party. Familiars can make for great scouts and especially make a major difference in the early levels of the game.

The problem?

There aren’t any aquatic-themed familiar options.

With a little bit of work, you might be able to work with your DM to create a familiar that’s more thematically appropriate for your character.

Consider something that can also breathe underwater and maybe deal cold damage. If you can argue to get a little floating cuttlefish or something similar along with you for the journey, it could really capture the idea of scouting the surface world for your patron.

Mechanically, Pact of the Chain is a very solid option!

Pact of the Talisman

On one hand, the Pact of the Talisman can be useful for any Warlock who wants to play more of a supporting role for their party.

However, I’m putting this one in the “meh” category for the Fathomless Warlock.

When it comes to the ability to just lock down and overwhelm enemies, the Fathomless Warlock is a powerhouse. The Pact of the Talisman does provide some useful features and Invocations, but it just doesn’t really fit with what this subclass specializes in.

I wouldn’t say it’s bad, but I would say that you could do better if you’re looking to optimize.

Pact of the Tome

If you’re more of the patient type, the Pact of the Tome is an excellent option that can really pay off in the later levels.

The new cantrips that you gain with your Book of Shadows can be used to expand the utility that you provide for your party. Between Eldritch Blast, your expanded spells, and your Tentacle of the Deeps, you’ve got damage covered pretty well.

This pact is a great way to widen what you’re able to do to contribute to the party’s efforts without spreading yourself too thin.

Focus on spells and invocations to help you lock down and punish enemies while you control the battlefield like an orchestra conductor… with tentacles… and the ability to fire eldritch blasts…

Well, that’s a terrifying mental image…

Anyways…

I’d say that the Pact of the Tome is ultimately the best Pact option for your Fathomless Warlock, though Pact of the Chain is an incredibly close second!

Also check out: Eldritch Invocations in 5e (Explanation + Best Options!)

Connections

So how do we connect your Fathomless Warlock to the game world?

Warlocks are very strongly defined by the “push me, pull you” effect of their Patron. It’s not just about what your character wants – you have to also make sure you’re keeping your Patron happy!

I think the Fathomless Warlock has possibly the easiest time furthering their Patron’s will of the other options. Somewhere beneath the waves, a powerful being is biding its time and you are serving as its eyes and ears to help it learn about the world above its watery domain.

From there, the possibilities are endless. What led to you encountering this being? Were you shipwrecked and it saved your life? Did you grow up in a seaside village that worshipped and revered this being?

When push comes to shove, are you loyal to your patron or is this simply an arrangement of convenience?

Most importantly, what does this Fathomless entity have that you want?

Think about these kinds of questions when you’re building your character. If you need some extra inspiration, check out my guide to the Warlock Patrons!

Is the Fathomless Warlock Good?

The Fathomless Warlock is a good option for players who want to focus on damage and controlling the combat. You get a ton of features and options to help you with both of these goals in addition to some extra utility.

More than anything, I love the theme and flavor of the Fathomless Warlock. If you’re doing a campaign with lots of naval and underwater elements, it’s a must-pick. Otherwise, it’s still a solid option in most campaigns.

All in all, I’d say that the Fathomless Warlock is definitely an option worth considering for your next character!

Want to see how the Fathomless stacks up against the other Warlock Patrons? Check out the full Warlock subclass ranking here!

Conclusion – Fathomless Warlock in D&D 5e Guide

Of all of the Warlock Patrons, the Fathomless is probably the most unique. There’s no shortage of ways that you can take it, and it’s hard to imagine one of these characters not bringing a ton of value to nearly any party!

The Warlock class in general has gotten a lot of love in 5e, but the Fathomless has done well in carving out its own name.

Hopefully, this guide has been helpful to you!

Do you still have questions or want to share your experience with the Fathomless Warlock? Say hi in the comments!

While you’re down there, don’t forget to sign up for the Tabletop Joab newsletter to get regular updates on all the latest tips, tricks, news, and more for D&D 5e!

You can also follow me on Facebook and Twitter.

If you found this article helpful and want to support the site, you can buy me a coffee here! (It’s not expected, but very appreciated!)