Kenpachi

When a barbarian takes up the Kenpachi archetype, changes to their body begin to manifest in ways some may consider beyond human. A world can only host a single kenpachi master at a time. For if more than one exists, the immediate goal of the kenpachi's is to find the other with the title and slay them. To be a Kenpachi requires you to defeat the previous in combat, others contesting for the title could be other archetypes. But if they successfully slay a kenpachi, they themselves become the kenpachi. 

Blood Lust

Starting when you choose this path at 3rd level, Whenever you slay a creature with a melee attack, you regain any expended reactions.

In addition, While in combat with a single creature, you gain advantage on attack rolls against that creature as long as you are the only one attacking it. If the creature is engaged by another creature, the enemy creature gains advantage against all other targets except you and you gain disadvantage on attacks against any other target other than the single creature. 

Alternatively, While in combat with many hostile creatures, whenever you rage. You can project a burst of blood lust in a 30ft radius. Each creature (friendly, and hostile.) Must succeed a Wisdom saving throw. (DC= 10+Prof+Str or Charisma. Your choice.) On a failed Save, Each creature is under the effects of Enemies Abound, without it being considered a spell. Creatures affected by this blood lust gain advantage to attack rolls, but disadvantage to saving throws. If the creature effected targets the kenpachi however, they lose disadvantage on saving throws.
(Blood lust is not considered a charm or fear effect, thus creatures immune to charm or fear effects are still effected.)


This ability can be used a number of times equal to your proficiency modifier.

Not Deep Enough

At 3rd level, While raging, you can use a reaction against a Ranged Melee Weapon attack, Melee Weapon attack, or Touch spell attack. You can use a reaction to reduce the damage by 1d12+Con+Barbarian Level. The damage you reduce is calculated AFTER resistances, but before damage is applied. If you reduce the damage to 0, as part of the the reaction you can push the attacking creature (if they are in melee reach.) 15ft away and knocked prone. 

additionally, you gain advantage on intimidation, persuasion, and deception checks against that creature for the next 24 hours.
With intimidation checks, you can inflict the frightened condition with a successful check.
With the Persuasion or Deception checks, you can inflict A short term madness effect. Kenpachi rolls 2d100, choosing one of the rolls to apply the result of to the creature.

Getting Serious

Starting at 6th level, your blood lust has reached its evolution. While attacking a creature, if you choose to do it non lethal damage, you can double the damage dice of your weapon. If the weapon is a dedicated weapon, the damage can be lethal or non lethal. 

When you reach 14th level in this class, a Dedicated weapon deals its maximum damage potential on each hit. If the weapon is not a dedicated weapon, you can roll twice for damage and take the higher of the two rolls. 

Exhilaration

At 10th level, Battle has painted its mark upon your soul, so much so that even in death you are still a force of nature.

In the event you are reduced to 0 hit points, you can make a constitution saving throw. DC=13. On a successful save, you regain 1 hit point, and can immediately roll any unspent hit dice. These hit points are considered temporary hit points for their duration. If you are reduce to 0 again, the DC increases by 2 for each trigger. If you are reduced to 0 hit points, and have no hit dice left. The final effect of Exhilaration is revealed.

While Raging, at 1 hit points, with no hit dice remaining the next successful attack with a dedicated weapon, you can replace your strength modifier on your dedicated weapon, with your strength score. If the attack misses, any hostile creature in melee can immediately use its reaction to make a melee attack if it choses too. If the attack of the hostile creature in melee misses, you regain any expended reactions and can immediately use it to make a final attack attempt.

This ability can be used a number of times equal to your proficiency modifier.

True Kenpachi

Beginning at 14th level, Your power has reached a pinnacle point. Marks of the Kenpachi begin to manifest and grant you abilities others would envy.

When you reach 14th level in this subclass, you gain a passive regeneration. Each turn while under half health you regain a number of hit points equal to the maximum result of your barbarian hit dice + con modifier.
In addition, you become immune to slashing, piercing, bludgeoning damage from non magical weapons, as well as resistance to force, thunder, and fire damage.

While under the effects of rage, blood lust, using a dedicated weapon you gain the ability to empower yourself to new level, however it comes with a cost. 
You may choose 1 boon, from the boon list to gain the benefit of it permanently, however in gaining this boon permanently. The next time you are reduced to 0 hit points, cannot use the Exhilaration. Your soul instead transfers into a dedicated weapon (if you have one.) or whatever weapon you are weilding. 

If a barbarian or kenpachi slays you, they can pick up the dedicated weapon. A barbarian that isn't a kenpachi, immediately becomes a kenpachi

You retain your mental a attributes as a sentient weapon. Work with the DM to build the benefits of the type of weapon you will be. (Good example is black razer, or craven edge.)