Path of the Hulking Berserker

Sometimes, the rage inside of a barbarian manifests on it's own, transforming them into a mindless killing machine, unable to discern friend from foe. The Path of the Hulking Berserker is a path of uncontrollable fury causing fear to friend and foe alike.

Uncontrolled Fury

At 3rd level you can enter an Uncontrolled Fury. This ability cannot be electively used, and is automatically activated when either A) your health has fallen below 25% of Max HP, or is in a situation that death is imminent from a non-attacking source (such as falling from a great height or a large object is about to fall on you) or B) someone that you have close relations with (lover, relative, close friend, etc. [DM's digression]) has fallen unconscious.

In this state, in addition to the normal bonuses of Rage (and uses 1 use of the ability if not already raging) you grow 1 size category (as with an Enlarge spell) and gain +10 movement speed, can jump double the normal length and height (as with the Jump spell), +4 temporary hit points per hit dice, advantage on Con based saves and ability checks, and triple the Rage bonus damage.

You also gain the Tavern Brawl feat while this Fury is active, with unarmed attacks dealing d8 damage (due to increased size). You cannot use weapons during this time (aside from makeshift weapons as with the Tavern Brawl feat) and drop anything being held in your hands. You also gain the Grapple feat. You cannot perform any actions except move and attack. All attacks in this form are Reckless Attacks (Advantage on attack rolls, attackers get advantage on their attacks against you.)

You cannot discern friend from foe in this form, and will attack the most threatening thing close to him. Generally you can target enemies first (as they are more threatening to you), but if there are none around, or too far away then friends are targeted (if an enemy is within range to move and attack in the same round, the barbarian will attack them, if not and an ally is within range, the ally is attacked). An ally can attempt to hide if they have proper cover to do so. If there is nothing to attack, then the barbarian will move at maximum run speed to find a new target.

You have disadvantage on Intelligence checks and saving throws.

Uncontrolled Fury cannot be willingly cancelled. The only way it can end is if 1) you fall unconscious 2) If you attack a friendly player or creature and knock it unconscious you can make a Wisdom saving throw (DC 12) to end the Fury 3) a close ally (lover, family, close friend etc. (DM approval)) can attempt a Persuasion roll (DC 8 + Proficiency bonus + your Wisdom modifier). If the ally succeeds, the rage ends.

You cannot enter an Uncontrolled Fury again until you heal above the 25% health threshold. Upon ending, incur 1 level of exhaustion.

Mindless Rage

Beginning at 6th level, you can’t be charmed or frightened while raging. If you are charmed or frightened when you enter your rage, the effect is suspended for the duration of the rage.

Intimidating Presence

Beginning at 10th level, you can use your action to frighten someone with your menacing presence. When you do so, choose one creature that you can see within 30 feet of you. If the creature can see or hear you, it must succeed on a Wisdom saving throw (DC equal to 8 + your proficiency bonus + your Strength or Charisma modifier (player chooses)) or be frightened of you until the end of your next turn.

On subsequent turns, you can use your action to extend the duration of this effect on the frightened creature until the end of your next turn. This effect ends if the creature ends its turn out of line of sight or more than 60 feet away from you. If the creature succeeds on its saving throw, you can't use this feature on that creature again for 24 hours.

During Uncontrolled Fury or Hulking Rage, this happens automatically to all enemies at the beginning of your turn.

Hulking Rage

Starting at 14th level, you can enter an Uncontrolled Rage willingly. When willingly entered, you can discern friend and foe, and can use weapons (you still cannot take any actions aside from move and attack). You can end the rage prematurely by making a Wisdom Save (DC 15), although the exhaustion effects still apply.

Uncontrolled rage can still happen unwillingly, and the original effects apply.  If a situation happens that would normally put you in an Uncontrolled Rage while you are in a Hulking Rage (such as reaching low HP), you stay in the Hulking Rage instead.