Path of Thunder

Path of Thunder barbarians learn how to harness, channel, and even produce electricity in their bodies, enveloping themselves in a defensive aura, dealing electrical damage with their attacks, and augmenting their bodies with the overflowing energy.

Because of this, those who follow the path of thunder cannot wear any metal armor or weapons, as it would disrupt the flow of electricity in their bodies. Instead, they use the energy as both offense, and defense, increasing their strength, speed, and resistance. 

Channel lightning

When you enter rage, you unleash the thunder within. You are unable to wear metal armor or wield any weapons, but your unarmed attacks deal an additional 1d4 thunder damage, and you gain advantage against enemies wearing metal armor, or are made of metal. Additionally, you gain Lightning Charges equal to your proficiency. You restore charges equal to half your proficiency when entering a rage state, and all of them with a short rest. You can spend these charges to perform the following actions:

Thunder Strike. When hitting an enemy with a melee unarmed attack, you can spend any number of charges to deal an extra 1d8 lightning damage for each charge spent. If the enemy is wearing metal armor, or is made of metal, your attack has advantage.

Lightning Rebuke. When hit by an attack, you can spend one charge to use your reaction to retaliate if the enemy is within 5 feet of you, or 10 if they are wearing metal armor, or are made of metal, dealing 1d10 lightning damage.

Thunderstep. As a bonus action, you can spend one charge to envelop yourself in a cloak of lightning and charge 20 feet in a straight line. Creatures who come into contact with you must perform an athletics check against you. If they fail, they are shoved aside - either left or right, to your choice - and take 1d10 lightning damage, and you continue to move forward until you reach the end of your path, or an obstacle you cannot pass through. If they succeed on the check, you cease your advance, and they take half damage. If you haven't moved, you may spend all your movement to extend the range of your charge to up to 60 feet, but if you fail the athletics check, you'll be knocked prone.

Thunderborn

You learn how to harness and control the power of the Thunder within, becoming one with it.

Lightning damage now heals you instead of damaging you, and for every 10 damage you would have taken this way, you restore 1 lightning charge. On top of that, when attacking an enemy who is resistant to lightning damage, they take lightning damage from you normally as if they were not resistant, and if they are immune, then they take damage is if they were only resistant instead.

Overload

You unleash the full might of your stored energy at once, by expending all your lightning charges, supercharging yourself with electrical power. The following bonuses last until your rage ends:

Any creatures who comes into contact with you, even through a medium - such as a weapon they are holding, a rope, or another creature they are in contact with - takes 2d10 lightning damage. If you enter a body of water up to 30 feet in area, all creatures within take this damage upon entering the area, and at the start of each of their turns. If the water is more than 30 and up to 60 feet in area, they take half damage. Beyond that, your electricity disperses too much and you're unable to use it, and you begin to discharge energy uncontrollably, losing 3 turns worth of rage each turn.

You can spend an ammount of your movement to charge twice that distance in a straight line. If you come into contact with a creature, they must perform an athletics check against you. On failure, they are shoved aside, either left or right, and knocked prone, and you continue to charge forward. If you have charged at least 30 feet, and succeed the athletics check, you deal an additional 2d10 thunder damage against them, and they are shoved 30 feet directly away from you instead.

You may spend 2 turns worth of your rage state to unleash a bolt of lightning against an enemy up to 30 feet away. They must perform a DC15 dexterity save, or take 4d10 lightning damage, half as much on a failure. For every extra turn of rage you spend, you increase this damage by 1d10. Enemies wearing metal armor, or who are made of metal, automatically fail this save.

You may end your rage earlier, and unleash a devastating explosion of electricity in a circle 40feet around you. For every remaining turn of rage you had before doing this, creatures caught within the radius take 1d10 lightning damage, or half as much on a successful DC15 dexterity save. Enemies wearing metal armor, or who are made of metal, automatically fail this save.

When your rage ends after entering this state, you gain a point of exhaustion.

Thunder Destruction Wave

While in overload state, as an action, you may spend four turns worth of fury to unleash a devastating beam of electrical energy 120ft in a straight line. The beam is 10 feet wide, and enemies must roll a DC20 dexterity saving throw. Upon success, they take 20d6 lightning damage. Upon failure, they take an additional 20d6 thunder damage.