Path of the Diabolical

Some barbarians have been touched by fiendish entities, whether they consort with these foul creatures or have been scarred in life-changing events, their dark influence has warped their fighting making them able to envelope themselves in the aura of the Lower Planes and utilise it's twisted powers as they channel their wrath. When a barbarian who walks this path rages, they are bringing forth those fiendish influences onto themselves ready to deal with the consequences that may entail soon after.

Tainted Form

3rd-level Path of the Diabolical feature

When you enter your rage, you reveal the fiendish influences within you. Until the rage ends, you gain resistance to fire damage and your melee weapon attacks deal an additional 1d4 fire damage.

Each time you rage ends early you must make a DC 10 Charisma saving throw unless you're knocked unconscious. On a failed save, your rage continues and you lose the ability to distinguish friend from foe, regarding all creatures you can see as enemies. On a success, your rage ends.

Each time you succeed the saving throw, the DC increases by 5. When you fail the save or finish a short or long rest, the resets to 10.

Eyes of the Blasphemer

3rd-level Path of the Diabolical feature

You gain darkvision out to a range of 60 feet. If you already have darkvision, its range increases by 30 feet.

When you reach 6th level, you can see through magical darkness out to the same range.

Sinner's Presence

6th-level Path of the Diabolical feature

When you enter a rage, every creature you choose within 10ft must succeed a Wisdom saving throw (DC equal to 8 + your proficiency bonus + your Constitution modifier) or be charmed or frightened by you (your choice) until the end of your next turn. On subsequent turns, you can use your action to extend the duration of this effect on the effected creatures until the end of your next turn. 

While a creature is charmed in this way, it is compelled to move toward you and creatures have advantage on attack rolls against it. This effect ends early if the creature takes any damage from you.

While a creature is frightened in this way, it is compelled to move away from you. When out of line of sight from you, the creature can attempt the saving throw at the end of its turn.

The range increases when you reach certain levels in this class, increasing to 20ft at 10th level and 30ft at 14th level.

Fiendish Demise

10th-level Path of the Diabolical feature

As a reaction when you reduce a hostile creature to 0 hit points, you force a number of creatures equal to your Constitution modifier (minimum of 1) within 30ft to make a Constitution saving throw (DC equal to 8 + your proficiency bonus + your Constitution modifier). A creature takes 5d8 necrotic damage on a failed save, or half as much on a successful one. If you reduce one or more creatures to 0 hit points in this way, you regain a number of hit points equal to your Barbarian level. While you are raging, creatures who fail this save can't regain hit points until the end of your rage.

You can use this feature a number of times equal to your proficiency bonus, and you regain all uses at the end of a long rest.

Profane Fury

14th-level Path of the Diabolical feature

When you enter a rage, you sprout fiendish bat wings granting you a flying speed equal to your walking speed. Additionally, while raging you gain immunity to fire damage.