Path of Adaptation (VoA)

In the Northern-East Territories there is a chaotic states ruled by an arena system called Free Utragbin States, in this territories endurance and vitality is the most importante abilities for surviving or winning combats or wars, in the past the rulers of this states trained very special warriors who expertised about the chaotic change of the battle field and Adaptation of battle. In this times there is not so many of them, but they are very strong like a mighty mountain.

(This subclass can be an option if you're playing in Void of Ages Campaign Setting)

Furious Regeneration

When you choose this path at 3rd level, each starts of your turn while you are raging you can restore hit points equal to your proficiency bonus, and if you targeted by a healing spell or effect you can restore additional hit points equal to your Constitution modifier.

Mobile Adaptability

As an action you can change your 25 feet of Walking speed to Swimming speed, Climbing Speed or Burrowing speed until the start of your next turn. You can use this feature equal to your proficiency bonus per long rest.

Chaotic Endurance

Starting at 6th level, while you are raging you gain additional a +1 bonus to your armor class and all of your saving throws, also you can use you reaction to gaining resistance to one coming attack until start of your next turn, but when you use this ability you must roll a contitution saving throw against DC of 10 + Target's Ability Modifier used for attack, if you fail the roll you get 1 level of exhaustion. You can use this feature once per rage.

Battlefield Acupuncture

At 10th level, you can make a rituel for 1 minute to gaining affect and clearing your negative energies, when you did this ritual you can decrease 1 level from your Exhaustion level (if you had), also you can restore 1d4-1 hit die of your barbarian class.

Steel Flesh

At 10th level, you gain resistance to poison damage type also you gain advantage to your Constitution saving throws against Poisoned and Diseased conditions. Also your Furious Regeneration ability starts to heals equal to twice of your proficiency bonus instead of your proficiency bonus.

Primal Adaptability

Beginning at 14th level, you can use your barbarian class hit dices (1d12 + Constitution Modifier) as a reaction for decreasing upcoming damage, you can use 2 of your hit dices in one turn.