The Leviathan

Your patron is a Leviathan, a mighty sea beast that is said to seize control of storms and lay waste to coastal settlements and cities. Such a creature destroys what it pleases, when it pleases, and as such it is quite rare that it will enter pacts with warlocks. These capricious beings may sometimes choose heralds of their arrival, those who spread the word of the power that stirs beneath the waves. Krakens are the most common beings to forge a pact of this kind.

Expanded Spell List

The Leviathan lets you choose from an expanded list of spells when you learn a warlock spell. The following spells are added to the warlock spell list for you.

1st - thunderwave, fog cloud

2nd - gust of wind, misty step

3rd - fly, call lightning

4th - ice storm, watery sphere

5th - conjure elemental, maelstrom

Storm Herald

Beginning at first level, when you hit a creature with a weapon attack, spell attack, or a creature fails a saving throw against one of your spells that targets only one creature, you can cause a bolt of lightning to strike the target, forcing it and every creature within 10 feet of it to make a Dexterity saving throw. On a failed save, the creature takes 1d6 lightning damage, or half as much on a successful one. This damage increases to 2d6 at 5th level, 3d6 at 10th level, 4d6 at 15th level, and 5d6 at 20th level.

You can use this feature a number of times equal to half your Charisma modifier (minimum of 1), and regain all expended uses after finishing a short or long rest.

Lightning Conduit

Starting at 6th level, you become immune to lightning damage, and cannot die as a result of drowning, although you can be reduced to 0 hit points as a result of being unable to breathe. If you are reduced to 0 hit points as a result of being unable to breathe, you are immediately stabilized as the spirit of the Leviathan enters your body and prevents your demise.

In addition, whenever you deal lightning damage to a target, you can reroll a number of damage dice equal to your Charisma modifier, and choose the result of either roll.

Stormcaller

By 10th level, the spirit of the Leviathan gives you an unerring connection to the storm. You always know what the weather will be like in the next 12 hours, and can conduct a 1 hour long ritual to call a tempest to your location. Throughout the ritual, dark storm clouds visibly gather over your location. When the ritual is complete, an intense storm forms over the land in a 1 mile radius, or a 5 mile radius if you are at sea. The storm lasts a number of hours equal to your warlock level, and cannot be ended early. While the storm lasts, driving rain and high winds persist, causing any ranged attack to suffer disadvantage. If a creature with a flying speed is caught in the storm, its flying speed becomes 0. The wind and rain may damage objects such as trees and manmade structures at your DM's discretion. Lighting also periodically strikes while the storm lasts.

You may use this feature once, and regain its use after completing a long rest. You cannot regain the use of this feature while a storm created by it is currently active.

Undertow

Beginning at 14th level, you gain the ability to become a rushing surge of water and overwhelm your enemies.

When you take the Dash action, you can choose to triple your walking speed instead of double it. If you do so, you become one size larger, do not provoke opportunity attacks, and gain the ability to move through other creature's spaces for free. Any creature whose space you move through in this way must make a Dexterity saving throw against your spell save DC. On a failed save, the creature suffers 8d6 bludgeoning damage and begins to move with you as it is swept away in the raging current. On a successful save, the creature takes half as much damage and is not dragged with you as you move. Any creature that is at least one size larger than you are while you are in this form automatically succeeds on this saving throw.

When your movement ends, you expel any creatures you swept away out of your space 5 feet in a direction of your choice and then morph back into your regular form. Every creature need not be expelled in the same direction. If you expel a creature into a wall or a similar hard surface, that creature takes 8d6 bludgeoning damage as they are slammed against the surface. If you end your movement adjacent to a door or other object, that object also takes 8d6 bludgeoning damage as the surging riptide slams against it.

You regain the use of this feature after finishing a short or long rest.