Path of the Stormfury

*This is subclass was created by u/lolasredfoot, just with my own personal tweaks added in. Adjusted damage for Mantle of the Storm.*

You have chosen the Path of the Stormfury, or perhaps it chose you. Through some aberration or inexplicable phenomenon, your rage is somehow so potent it manifests itself through pure elemental energy. The tempests that break ships across treacherous bays, the storms that crack the sky with thunder and set forests ablaze with lightning, the blizzards that tear throughout the barren wastes all sing through your primal fury.

Fury of the Storm (lvl 3)

While you are raging, you become the embodiment of the elemental typing of your choice. On each of your turns while you are raging, the first hit against an enemy deals an extra 1d6+CON of damage of the same type as your rage element. The damage dice increases to a d8 at level 8, a d10 at level 13, and a d12 at level 18.

Atmospheric Aegis (lvl 3)

While you are raging, you can expend your reaction to increase the AC of an ally that you can see within 15ft by your CON modifier.  You may use this ability a number of times equal to your Proficiency Bonus per long rest.

Surging Storm (lvl 6)

Your movement speed increases by 5 ft while you are raging.

Devouring Tempest (lvl 10)

When you are forced to make a saving throw as a result of a spell, you may choose to change the type of save to a CON save.

On a success, you absorb the spell. If the spell does a form of elemental damage, your next successful melee attack can add that damage and type to its attack. 
If the spell does not deal elemental damage or is a non damaging spell, your next melee attack instead deals 1d6 per level of the spell you just absorbed.

You may use this feature a number of times equal to your proficiency bonus and all expended uses refill after a long rest.

Mantle of the Storm (lvl 14)

Whilst your Mantle of the Storm is active, you may designate characters within 15 feet that will remain unaffected. While using Mantle of the Storm you may change your chosen element once per rage as a bonus action.

The Mantle has varying effects based on the chosen element:
 
Fire:

You erupt in a storm of flames.

When a creature starts its turn within your Mantle it takes 2d10 Fire Damage.
 
Cold:

You bring a blizzard wherever you walk, turning the ground into difficult terrain.

Enemies within 15ft must make a DEX save against your DC or be rooted in place (movement reduced to 0).  This effect occurs when a creature starts its turn within your Mantle.
 
Lightning:

You summon a torrent of lightning that engulfs and surrounds you.

When a creature within your Mantle hits you with a melee attack, they must make a CON save or take an amount of damage equal to the damage dealt and half damage on a success.

Thunder:

You conjure the roaring forces of  Tidal Storm.

When you hit a creature that is within your Mantle with a melee attack it takes an additional 1d6 Thunder damage. Also if the creature is Large or smaller you can choose to have it make a STR saving throw or be pushed back 10ft and knocked prone.

 

All conditions last for a number of minutes equal to your CON modifier. If a target makes a save and resists a status condition, they are immune to the condition for the duration of that rage.