Warlock Patrons: The Fathomless

Guide by Sam West, Twitter:@CrierKobold

Maybe you love sailing and boats, and are fascinated with the mythology and mystery around the creatures of the deep. Maybe something deep inside you just needs to scream “RELEASE THE KRAKEN”. In any case, the Fathomless Otherworldly Patron is here to satisfy your nautical monstrosity fantasies with some slippery tentacles and underwater boons.

Fathomless warlocks get an iconic tentacle to slap people around with that will largely identify them; beyond that, they get some decent damaging and summoning magic, an incredible re-flavor of a busted 5th level spell, and a robust kit built around the tentacle to empower you in and out of water. Any warlock build can thrive with a Fathomless patron, and shine even brighter in seafaring adventures.

1st-3rd Level: Tentacle of the Deep, Gift of the Sea, and Expanded Spells

Tentacle of the Deep is the feature that defines the bulk of Fathomless warlocks. Mechanically, it's pretty straightforward: you spend a bonus action to make a 10 ft. long tentacle for a minute that makes a bunch of 1d8 cold damage spell attacks for you when summoned and subsequently for a bonus action. It scales at your 10th level in warlock up to 2d8, and can be moved about with the same bonus action used to attack 30 feet at a time. Plus, you can summon it multiple times a long rest equal to your proficiency bonus, making it a feature that scales with total level as well.
Having a bonus action attack option out the gate makes it so Fathomless warlocks rarely lack ways to weaponize their bonus action. You’re going to feel great in the frontline and backline sending your tentacle around beating things up. This will feel close to Spiritual Weapon, and that’s a ringing endorsement for a 1st level feature you get multiple uses of.
Gift of the Sea is mainly a ribbon feature, something that adds thematics to your character without having a huge improvement on gameplay. That is, unless you’re playing at a seafaring game where underwater combat is common; in that instance, a 40 ft. swim speed and waterbreathing are critical to being high performing under the waves. At its worst, it’s a flavorful improvement alongside a bonkers good other 1st level feature; at its best, it’ll define you as the best underwater combatant at 1st level.
Create or Destroy Water always has a home on character sheets looking to try to mess around with physics in D&D. It does technically scale with spell level, meaning your Pact Magic slots get slightly more use out of it than many 1st level spells, but you really don’t need Create or Destroy water unless you’re trying to create a bunch of water pressure or coming up with some other nonsense to ask your DM wacky questions about how magically creating 10 gallons of water affects the world, or if a goblin with his mouth open qualifies as an “open container” for destroy water.
Thunderwave is the other 1st level spell option you get, which is aggressively mediocre. Its does fine enough damage, scales with spell level, but still isn’t something you’ll probably want to be spending your few Pact Magic slots on. It does enough damage at 1st level that you’ll probably find some uses for it in the first few levels, but past 3rd level, you can do better.
Gust of Wind is normally a tool I like to highlight, as it can be a critical element of area of effect damaging builds looking to push creatures into damaging areas. On warlocks, however, it is competing for your upper level Pact Magic slots and eating your concentration. This makes it something you can mess around with at 3rd and 4th levels and get some value out of it, but probably don’t want to ever be casting after that.
Silence, on the other hand, is a spell that, even when you have to spend spell slots over 2nd level on it, can be a critical way to get an advantage in a fight. Silence is a way to lock down a 20 ft. sphere area to prevent spellcasting; this can make some otherwise lethal threats harmless. As long as somebody else can keep the demilich or shaman in the bubble, this can debilitate them, as the majority of spells in the game require verbal components. Using it for its utility is going to fall off pretty quickly past 3rd level, but having it on your sheet as a silver bullet for some monsters is a real reason to consider keeping this around.

4th-7th Level: Oceanic Soul, Guardian Coil, and More Expanded Spells

Oceanic Soul is the most decorative ribbon feature you can get, and not much else. This makes you like Aquaman, giving you a way to just ignore the communication problems when speaking underwater. It is like a Comprehend Languages while under water. Sometimes you’ll dunk the goblins head in a tank with yours to talk, which will undoubtedly be hilarious, but otherwise this is resistance to cold damage, and that’s not that exciting.
Guardian Coil, on the other hand, gives you a new reaction to play around with your Tentacle of the Deep, and makes you actually care about keeping allies near it. By keeping the tentacle around yourself or friends, you can constantly reduce incoming damage, round after round, by 1d8 when you get it and 2d8 at 10th level. This paired with the extra uses your getting from an increasing proficiency bonus will start to make the Tentacle a central element of most fights you’re going into. Going into battle with Thirsting Blade and a tentacle by your side will give you a free bonus action d8 damage attack each turn and a way to mitigate an incoming 1d8 damage from attacks on yourself and nearby other martial allies. Backline supporting or blasting warlocks slap this down next to their paladins and barbarians for a similar effect, but without risking their own health. You can even just stick it near your summoned ally obtained through one of the Summon spells or Conjure Elemental. It's a sweet feature, regardless of what you’re spending your actions on.
Lightning Bolt FINALLY gets its time to shine, as warlocks don’t get access to Fireball! Now, if you want that sweet, sweet, 8d6+1d6 per spell level above 3rd, you’re going to have to line up as many baddies as possible to get the payoff! Its absolutely worth it; this is a huge damage option when you need it. Even with your limited spell slots as a warlock, even when needing to forcibly up-cast it, Lightning Bolt delivers a huge amount of damage at once. Its an amazing option to get.
Sleet Storm is a conditional giant area of effect lockdown tool that drags fights to a halt. It costs your concentration, too, making it a bit tricky to use in combination with other long duration concentration effects you tend to care about. Still, sometimes you need a 40 ft. radius, 20 ft. tall area of heavy obscurity, difficult terrain, and constant saves against falling prone that can end concentration effects. This will likely be a spell you’ll be glad you had a few times per campaign, but not something you’ll regularly be casting, especially given that it has no up-cast bonus.
Control Water is a nifty 4th level effect that offers four options in one: Flood, Part Water, Redirect Flow, and Whirlpool. Its main requirement is there be water to use; in aquatic games, this spell is a homerun, offering some nifty tools for exploring the world and attacking enemies. Outside of that exact environment, this spell is way too niche to pick up.
Summon Elemental, however, is BONKERS good, as most summon spells are. It doesn’t even restrict you to water elementals, meaning you can flexibly get any of the four modes you want. It scales with spell level, makes multiple attacks, doesn’t even compete with your bonus action, and causes your DM to have to consider an entire other character engaging with their fights. It has an hour duration. It can have the amorphous trait, a fly speed, a burrow speed, a swim speed, and hits like a bus with two 1d10+8 or 9 attacks each turn. This spell will always be an excellent option to have.

8th-10th Level: Grasping Tentacles and 5th Level Expanded Spells

Grasping Tentacles takes the spell Black Tentacles, gives you a free cast once per long rest, and gives you temporary hit points equal to your level when casting it. As an extra bonus, your concentration also can’t be broken when using it, which is neat! Realistically, your concentration is already very competitive, so you likely won’t be spending that many of your actual Pact Magic slots on this. Getting a free cast of a solid area of effect restraining tool that deals mediocre damage is nice to have, though, especially with the free boost to your hit points. This is something you’ll probably use right after something breaks your concentration on a higher impact spell like Summon Elemental or…
Arcane Hand disguised appearing as a giant tentacle is one of the biggest thematic home runs I could ask for. Unfortunately, there is one major problem with it: it needs you to spend bonus actions on it for it to function. All of the modes you can get are great; it can grapple stuff, defend you, smack people around, and shove creatures huge distances. It competes with the bonus action you want to be regularly using, making it a bit clunky. It’ll often feel like something you’re casting in place of your Tentacle of the Deep. Why use this when you could have an elemental and a Tentacle of the Deep? If you like the fantasy of an upgraded Tentacles, this spell is the perfect upgrade for you. It just makes me a bit bummed out that it isn’t really that synergistic with the rest of the subclass.
Cone of Cold is the final new spell you get access to; like a giant area cone of damage doing roughly the same damage as your Lightning Bolt? Cone of Cold is for you! This will often be a replacement for Lightning Bolt, as the both always compete for the same spell slots and this hits a “better” area. You probably don’t need both, but having one or the other gives you a high impact, high damage, area of effect tool you’re going to regularly want.

14th Level: Fathomless Plunge

Fathomless Plunge caps off the subclass at 14th level with a small departure from the regular tentacle based improvements offered, instead giving you a mile-long group teleport feature. I adore this thematically; having an ancient creature of the depths swallow the party and spit them out in a body of water is rich in flavor. This is no Teleport, nor can it really be asked to be. At its best this will be a tool to take you out of danger and to a safer body of water. There will almost always be pools lying around most games large enough to use this; you’ll be highly encouraged to scout out areas around a dungeon prior to delving. From there, this can be an instantaneous escape from peril, a get out of jail free card that recharges on short rest. Dedicated notetakers and cartographers will start charting out the varying bodies of waters around to know which are the best spots to teleport to. It is a great tool to get, and a thematically rewarding option to play with.

All Together

Fathomless warlocks play all around their Tentacle of the Deep; it's their core identity. They leverage grappling tentacles and bonus casts of Black Tentacles to get big areas of control and damage. Their expanded spell selection is excellent past 3rd level, granting characters access to some truly potent magic that can make a big impact on the game. Grasping Tentacle encourages better tentacle placement and management, pairing well with both ranged and melee warlocks, and Fathomless Plunge is a great short rest recharging mass teleport when you need it. The Fathomless patron is a homerun thematically, mechanically, and will work great on any character who doesn’t want to commit to a different bonus action than slapping people around with a tentacle of the deep.

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