Path of the Molten

Many people can see the similarities between a barbarian and a volcano. Some barbarians take those parallels a step further, treating their rage much like an eruption: allowing it to simmer and boil over until it erupts into a fiery show of power and fury.

Barbarians that take up this path are often found living in close proximity to such a volcano, though it need not necessarily be active. Other barbarians may have been shown druidic magic that allows them to channel the primal power of the world as molten rock and fire.

Eruption

You've learned to temper and nurture your rage, allowing it to build up for an even more spectacular eruption. Whenever you take damage while not raging, you temper your fury for later use. This condensed anger is known as heat. You can store a maximum number of heat charges equal to your Constitution modifier (minimum of 1). You lose all charges of heat after a long rest.

When you enter your rage, you can consume all charges of heat in a fiery explosion. Creatures within 10 feet of you must make a Dexterity saving throw. The DC for this save is equal to (8 + your Constitution modifier + your proficiency bonus). On a failure, a creature takes 1d6 fire damage per heat charge consumed. When you erupt in this manner, you can choose any number of creatures to succeed on the save.

The size of the eruption damage dice increases when you reach certain levels in this class: at 5th level (d8), 11th level (d10), and 17th level (d12).

Volcanic Empowerment

When you erupt into your rage, some of the volcanic power lingers, granting you additional benefits. When you enter a rage that consumes heat charges, you can choose to benefit from one of the following effects. The chosen effect lasts until your rage ends.

Charred Skin

Molten rock encases your skin, protecting you from attacks. Your AC increases by 1. While you are grappling a creature, you can choose to deal 1d6 fire damage to them at the start of your turn. Additionally, if you are grappled by a creature, they take 1d6 fire damage at the start of their turn.

Scorching Strikes

Your attacks are infused with lava, burning your targets for further damage. Whenever you hit an enemy with a melee weapon attack, you deal an additional 1d8 fire damage. You can also choose to replace your weapon's normal damage type with fire damage whenever you attack.

Veins of Magma

The blood beneath your skin burns as hot as magma beneath the earth. You gain resistance to fire damage and ignore negative effects of cold weather environments. Whenever you are hit by a melee attack, the attacker takes fire damage equal to your Constitution modifier. While you are raging, this damage increases to twice your Constitution modifier.

Additionally, you gain further control of your eruptions. Your eruption now has a radius of 30 feet, and when you choose creatures to succeed on the save against your Eruption feature, those creatures take no damage instead of half.

Tectonic Upheaval

Your mastery over your fiery rage has reached new heights. You gain a bonus to damage rolls and saving throws equal to the number of heat charges you have. In addition, the AC bonus granted by the Charred Skin effect increases to +2, and the fire damage provided by the Scorching Strikes effect increases to 2d8.

Your eruptions now also leave burning aftershocks after the initial eruption. For 1 minute after consuming heat for a rage, you create molten earthquakes in a 30-foot radius centered on you. This effect follows you when you move, and acts as difficult terrain for creatures damaged by your Eruption feature. When a creature ends its turn within the area, you can choose to force it to make a Strength check against your Eruption DC. On a failure, the creature is knocked prone and takes fire damage equal to your barbarian level + the number of heat charges consumed. On a success, a creature takes half damage and is not knocked prone.