Path of Purest Rage

Not all Barbarians need to channel their rage into primal connections, spiritual guidance, or other complex avenues. "Pure" Barbarians feel a blazing rage so intense, their bodies exceed the limitations of their flesh and body. These barbarians rarely see reason or strategy as part of a battle, opting to fight to their last breaths until their fury is quelled, or their foe is felled. They have little concern for their wellbeing or what their body is supposed to be capable of, and they will stop at nothing to demonstrate that their rage burns hot enough to destroy the realm with themself in it, and still remain ignited enough to reign chaos in their afterlife. Berserkers with nothing to lose, villains with abnormally tragic pasts, and denizens of chaotic planes with a capacity for pain more extreme than mortals call themselves "Pure" Barbarians.

Level 3: Carnage Incarnate

You can throw caution to the wind and your enemies through the flames. You can expend your Barbarian Hit Dice to fuel your attacks. When you use your Reckless Attacks feature and hit with a melee attack, you can expend and roll any number of your hit dice, up to half of your Barbarian level (rounded down), and add it to your damage roll as Fire damage or Force Damage. Additionally, when you hit an Object with an attack that expends hit dice, it is automatically considered a Critical hit, and you roll the maximum possible damage instead of rolling on your damage dice. Additionally, when you hit an Object with an attack that expends hit dice, it is automatically considered a Critical hit, and you roll the maximum possible damage instead of rolling on your damage dice.

Level 3: Rage Beyond Reason

You can charge headfirst into battle to exact your fury. When you activate your Rage, you can expend an additional use of your Rage to an Unbridled Rage. Unbridled Rage follows the same rules as your regular Rage, with these additional benefits:

Onslaught!  You have resistance to all damage except Force and Psychic damage. If a creature deals damage to you equal to twice your Barbarian level or more in a turn, you regard the creature that dealt the damage as your enemy, regardless of circumstance. On each of your turns, you must move as close to the creature as possible and take the Attack action, targeting that creature with melee attacks until the target is reduced to 0 hit points, or your Unbridled Rage ends. If multiple creatures deal sufficient damage to trigger this effect from you, choose the nearest enemy and continue taking the Attack action on each of your turns until all enemies have been reduced to 0 hit points or until your Unbridled Rage ends. If the enemy is not within reach, you must take the Dash action and move towards the nearest enemy.

Headlong!  You gain a bonus to your Speed equal to 10 times your Rage Damage bonus. Additionally, you can move through the space of another creature or object as though it were difficult terrain. When you do so, if it is a creature, it can use its reaction to roll a Dexterity Saving Throw, or forgo the Saving Throw. On a Success, the targeted creature can move to any unoccupied space within 5 of itself, avoiding your path of destruction. On a failed save, the creature takes Bludgeoning damage and is knocked prone. The damage is a number of d4s equal to your Rage Damage bonus. 
Any creatures that do not have any unoccupied space within 5 feet of them, inanimate objects, or any creatures that choose to forgo the Dexterity Saving Throw automatically fail the saving throw. A creature can take this damage only once per turn.

Unbridled Rage

Unbridled Rage follows the same rules as your regular Rage, with these additional benefits:

Onslaught!  You have resistance to all damage except Force and Psychic damage. If a creature deals damage to you equal to twice your Barbarian level or more in a turn, you regard the creature that dealt the damage as your enemy, regardless of circumstance. On each of your turns, you must move as close to the creature as possible and take the Attack action, targeting that creature with melee attacks until the target is reduced to 0 hit points, or your Unbridled Rage ends. If multiple creatures deal sufficient damage to trigger this effect from you, choose the nearest enemy and continue taking the Attack action on each of your turns until all enemies have been reduced to 0 hit points or until your Unbridled Rage ends. If the enemy is not within reach, you must take the Dash action and move towards the nearest enemy.

Headlong!  You gain a bonus to your Speed equal to 10 times your Rage Damage bonus. Additionally, you can move through the space of another creature or object as though it were difficult terrain. When you do so, if it is a creature, it can use its reaction to roll a Dexterity Saving Throw, or forgo the Saving Throw. On a Success, the targeted creature can move to any unoccupied space within 5 of itself, avoiding your path of destruction. On a failed save, the creature takes Bludgeoning damage and is knocked prone. The damage is a number of d4s equal to your Rage Damage bonus. 
Any creatures that do not have any unoccupied space within 5 feet of them, inanimate objects, or any creatures that choose to forgo the Dexterity Saving Throw automatically fail the saving throw. A creature can take this damage only once per turn.

Level 6: Supreme Bloodlust

Your hit dice fueled attacks are even stronger than before. When you expend any hit dice to fuel your attacks, you can add some additional benefits to the attack if you expend the minimum number of hit dice as specified in each of the following features. You can add any number of benefits to an attack as long as you expend the minimum number of hit dice required for each benefit. A creature can be affected by each Supreme Bloodlust benefit once per turn.

Brutalize! (1 Hit Dice) The target takes an extra 1d12 Bludgeoning, Piercing, or Slashing damage once per turn from any attack of those damage types until the end of your next turn.

Decimate! (4 Hit Dice) The target must succeed on a Constitution Saving Throw (DC = 8 + Prof Mod + STR Mod) or have Vulnerability to Bludgeoning, Piercing, and Slashing damage until the end of your next turn, regardless of any existing Resistances or Immunities. The affected creature can reroll the save at the end of their turn, ending the effect on a success.

Pulverize! (7 Hit Dice) The target has disadvantage on Saving Throws until the end of your next turn.

Disintegrate! (10 Hit Dice) If the target fails the initial Saving Throw against your Decimate feature, it has the Paralyzed condition until the end of your next turn. If it succeeds, it has the incapacitated condition, and its Speed is reduced by 20 feet.

Atomize! (13 Hit Dice) The target takes an additional 3d8 damage from all sources of damage until the beginning of your next turn.

Annihilate! (16 Hit Dice) If the target is bloodied before the end of your next turn after this attack, it is instantly reduced to 0 hit points. All creatures within 60 feet of this creature, including yourself, must succeed on a Dexterity Saving Throw or take Fire or Force damage equal to the rolls of your hit dice expended, taking only half damage on a success.

 

Level 10: Bottomless Pit of Rage

You gain a special pool of Hit Dice, which can be used for any normal uses of a Hit Die, or to fuel your attacks. This pool has a number of Barbarian Hit Dice in it equal to 2 times your Proficiency bonus. You regain any Hit Dice expended from this pool at the end of a Long Rest.  The maximum number of Hit Dice you can expend to fuel each attack is now half your Barbarian level (rounded down) plus your Proficiency Bonus.

Additionally, when you enter your Unbridled Rage, you can roll a number of Hit Dice equal to half your Barbarian level (rounded down) without expending the dice. You gain temporary hit points equal to the total of the roll.

Level 14: Rage Beyond Restraints

You've experienced such a hatred that manifests into rages unlike any others. While in your Unbridled Rage, you can expend an additional 2 uses of Rage to enter Transcendent Rage. This Rage cannot end under any circumstances, unless you regain the charges of rage that were expended to ender this Rage, or until you choose to end the rage. Transcendent rage follows the same rules as your regular rage with these additional benefits:

Heedless Violence:  Your anger rages stronger than your regard for your own safety. Reckless Attack is considered to always be active as long as you are in Transcendent Rage. One per turn, if you hit with a reckless attack, you can make the attack a Critical hit. If you use this feature to make an attack into a Critical Hit, the next attack to hit you before the start of your next turn is also automatically considered a Critical Hit. Additionally, if you have taken the Attack action on your turn, you can make an unarmed strike or melee attack as a bonus action.

Screech of Hatred:  Your anger rages stronger than you can suppress, unleashing itself in a shrill screech that terrifies both friends and foes alike. As a bonus action, unleash the sound of pure hatred from deep within, all creatures within 60 feet of you must succeed on a Constitution Saving Throw (8 + Prof. Bonus + STR Mod + Rage Damage Bonus) or gain the frightened condition. Bloodied Creatures that gain the frightened condition from this feature must immediately use their movement to move as far away from you as they can. They may use their action and bonus action regularly after they have used their movement to move away from you.