Base Class: Barbarian
Barbarians who walk the Path of the Elemental Herald have learned to channel the fury of the elements themselves, and are conduits of elemental expression and power. When in a fury, a barbarian of this path is surrounded by torrents of element energy, which these barbarians tap into to create powerful magical effects.
Elemental heralds are typically elite champions who may train alongside druids, rangers, and others sworn to protect the natural order. Other elemental heralds hone their craft deep inside regions wracked by the unfettered elements — in the frozen reaches at the world's end, or deep in the hottest deserts — attuning themselves to bring forth the elements' deadly message
Elemental Aura
When you select this path at 3rd level, you emanate a powerful, elemental aura while you rage. The aura extends 10 feet from you in every direction, but not through total cover.
Your aura has an effect that activates when you enter your rage Choose one of the elements listed below. Your aura's effect depends on that chosen element, as detailed below. You can choose a different element each time you enter a rage.
Acid
When this effect is activated and at the start of each of your subsequent turns while this effect remains, a creature of your choice in your aura takes a -1 penalty to attack rolls until the start of your next turn. The number of creatures you can choose increases when you reach certain levels in this class, increasing to 2 at 5th level, 3 at 10th level, 4 at 15th level, and 5 at 20th level.
Cold
When this effect is activated, each creature of your choice in your aura gains 1d4 temporary hit points, as icy spirits inure it to suffering. The temporary hit points increase when you reach certain levels in this class, increasing to 2d4 at 5th level, 3d4 at 10th level, 4d4 at 15th level, and 5d4 at 20th level.
Fire
When this effect is activated, you can designate any number of creatures you can see to be unaffected by it. When a creature enters the area for the first time on a turn or starts its turn there, it takes 1d4 fire damage. The damage increases when you reach certain levels in this class, increasing to 2d4 at 5th level, 3d4 at 10th level, 4d4 at 15th level, and 5d4 at 20th level.
Lightning
When this effect is activated, once per turn when you hit with a weapon attack, the target takes an extra 1d6 lightning damage. The damage increases when you reach certain levels in this class, 2d6 at 5th level, increasing to 3d6 at 10th level, 4d6 at 15th level, and 5d6 at 20th level.
Thunder
When this effect is activated and at the start of each of your subsequent turns while this effect remains, a creature of your choice in your aura gains advantage on its next attack roll or saving throw until the start of your next turn. The number of creatures you can choose increases when you reach certain levels in this class, increasing to 2 at 5th level, 3 at 10th level, 4 at 15th level, and 5 at 20th level.
Exclamation of the Elements
At 6th level, the elements grant you additional benefits even when your aura isn't active. At the end of a long rest, choose an element whose message you wish to bear until the end of your next long rest. Your appearance slightly shift towards the theme of your element, additional benefits are described below based on the element you choose.
Acid
You gain resistance to acid damage, and you have advantage on saving throws against poison. Additionally, you gain a climbing speed of 30 feet.
Cold
You gain resistance to cold damage, and you don’t suffer the effects of extreme cold, as described in the Dungeon Master’s Guide. Moreover, as an action, you can touch water and turn a 5-foot cube of it into ice, which melts after 1 minute. This action fails if a creature is in the cube You gain a swimming speed of 30 ft.
Fire
You gain resistance to fire damage, and you don’t suffer the effects of extreme heat, as described in the Dungeon Master’s Guide. Moreover, as an action, you can touch a flammable object that isn’t being worn or carried by anyone else and set it on fire.
Lightning
Lightning. You gain resistance to lightning damage. Additionally, you gain a flying speed of 15 feet.
Thunder
You gain resistance to thunder damage. Additionally, you gain a flying speed of 15 feet.
Elemental Escalation
At 10th level, the strength of your connection surges with power. Your Elemental Aura feature now extends 30 feet from you in every direction. Additionally, creatures of your choice that you can see in your aura gain the benefits of your Exclamation of the Elements feature, the element is determined by the element you chose for your Elemental Aura feature.
Elemental Apotheosis
At 14th level, the power of the elements inside you reach their pinnacle. You become the embodiment of the elements, unveiling stark changes to your appearance when you rage.
Additionally, you gain an elemental shield for the duration of your rage. Whenever a creature within 5 feet of you hits you with a melee attack, the shield erupts with the element of your choice. Choose acid, cold, fire, lightning or thunder, the attacker takes 2d6 damage of the type of your choice.
Finally, you gain access to the following reactions detailed below, using one of these reactions requires you to speak the element to power, use the rules for verbal components as detailed in Chapter 10 of the PHB for reference on their limitations.
Acid
When a creature that you can see within 30 feet of you makes an attack roll, you can use your reaction to roll 1d4 and subtract the number rolled from the creature's roll.
Cold
When a creature that you can see within 30 feet of you takes damage, you can use your reaction to grant them temporary hit points equal to 2d4 plus your Constitution modifier.
Fire
When a creature that you can see within 5 feet of you deals damage to you, you can use your reaction to cause a 15-foot cone of flame to erupt towards the creature. Each creature in the cone takes 3d4 fire damage.
Lightning
When a creature that you can see within 30 feet of you hits with a weapon attack, you can use your reaction to cause the attack to deal an additional 3d6 lightning damage.
Thunder
As a reaction to a creature you can see within 30 feet of you casting spell, you can use your reaction to force that creature to make a concentration check (DC equal to 2d4 plus your Constitution modifier plus your proficiency bonus) or the creature's spell fails and has no effect.