Fathomless Patron

You have plunged into a pact with the deeps. An entity of the ocean, the Elemental Plane of Water, or another otherworldly sea now allows you to draw on its thalassic power. Is it merely using you to learn about terrestrial realms, or does it want you to open cosmic floodgates and drown the world ?
Perhaps you were born into a generational cult that venerates the Fathomless and its spawn. Or you might have been shipwrecked and on the brink of drowning when your patron’s grasp offered you a chance at life. Whatever the reason for your pact, the sea and its unknown depths call to you.
Entities of the deep that might empower a Warlock include krakens, ancient water elementals, godlike hallucinations dreamed into being by kuo-toa, merfolk demigods, and sea hag covens.

Level 3: Fathomless Spells

3rd-level Fathomless feature

The magic of your patron ensures you always have certain spells ready; when you reach a Warlock level specified in the Fathomless Spells table, you thereafter always have the listed spells prepared.

Fathomless Spells

Warlock Level	Spells
3	Create or Destroy Water, Gust of Wind,, Thunderwave, Silence
5	Lightning Bolt, Sleet Storm
7	Control Water, Evard’s Black Tentacles
9	Bigby’s Hand(appears as a tentacle), Conjure Elemental

Level 3: Tentacle of the Deeps

3rd-level Fathomless feature

You can magically summon a spectral tentacle that strikes at your foes. As a Bonus Action, you create a 10-foot-long tentacle at a point you can see within 60 feet of you. The 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. You can summon the tentacle a number of times equal to your Charisma modifier (minimum once), and you regain all expended uses when you finish a Long Rest.

Level 3: Gift of the Sea

3rd-level Fathomless feature

You gain a Swim Speed of 40 feet, and you can breathe underwater.

Oceanic Soul

6th-level Fathomless feature

You are now even more at home in the depths. You gain resistance to cold damage. In addition, when you are fully submerged, any creature that is also fully submerged can understand your speech, and you can understand theirs.

Guardian Coil

6th-level Fathomless feature

Your Tentacle of the Deeps can defend you and others, interposing itself between them and harm. 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 plus half your Warlock level.

Grasping Tentacles

10th-level Fathomless feature

You can cast the Evard’s Black Tentacles spell without expending 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 ensures the spell’s resiliency. Your Concentration on the spell is only broken if you have the Incapacitated condition, and Concentrating on it does not prevent you from Concentrating on other Warlock spells.

Fathomless Tentacles

14th-level Fathomless feature

As an action you  can summon enormous spectral tentacles that burst from your surroundings, which grab you and up to 5 creatures of your choice that you can see within 30 feet of you. The tentacles move each creature within 120 feet of its starting position or 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 appearing in an unoccupied space within 30 feet of the others.
Unwilling creatures can make a Strength saving throw against your spell save DC to avoid being moved.

Once you use this feature, you can’t use it again until you finish a Short or Long Rest.