Path of One Mind
Those who follow the Path of One Mind were once singular in their focus of attaining greater strength in combat only to hesitate at where it found them: a small step from being a living incarnation of carnage and destruction that would kill for the pleasure of it, laying waste to all before them.
They now apply that focus to mastering themselves and ensuring none follow that treacherous path, even if it means cutting down one they consider a friend.
One Strike
3rd-level Path of One Mind feature
Your pursuit of strength has taught you to focus your fighting spirit into a single, devastating attack. The first creature you hit on each of your turns with a melee attack takes extra damage of the same type equal to two rolls of your Rage Damage die.
At 6th level, you deal this extra damage each time you make a melee attack. If you deal this damage to the same creature twice in the same round, it must succeed on a Strength saving throw (DC = 8 + your proficiency bonus + your Constitution modifier) or be knocked prone.
Breath of Nature
6th-level Path of One Mind feature
You've learned to take a moment to catch your breath, expelling regrets and reaffirming your fighting spirit. As a bonus action on your turn, or as part of entering a rage, you can expend a number of hit dice equal to up to half your barbarian level and regain hit points equal to the total rolled + your Constitution modifier.
You can use this feature a number of times equal to your proficiency bonus and must finish a long rest before you can do so again.
Boiling Blood
10th-level Path of One Mind feature
The lust for battle and the burning carnage that you've struggled to suppress becomes harder to ignore the closer you are to death. When you are below half your hit point maximum, you can cause your One Strike damage to become fire damage.
Additionally, your One Strike causes a gout of flames to burst forth in a 20-foot cone. Each creature in the cone must succeed on a Dexterity saving throw or take your One Strike damage as fire damage.
The ground in the cone ignites in flames and burns for a number of rounds equal to your proficiency bonus. A creature that moves into or ends its turn in a burning area takes fire damage equal to your Constitution modifier.
One Mind
14th-level Path of One Mind feature
Your singular focus has achieved the impossible, allowing you to unleash a blinding flash of blows with a single sweep of your weapon. You can use your action to make a flurry of strikes in a 15-foot cube originating from you.
Each creature in the cube must succeed on a Dexterity saving throw or take your One Strike damage. You can then make a single melee attack with advantage against a creature in the cube as a bonus action.