Bloodknife

he Infernal Legions have many soldiers, but none are more deadly than those known as Bloodknives. 

The elite warriors of the Nine Hell's Armies, Bloodknives enhance their significant skills by drawing from their own vitality, gaining access to sinister abilities beyond their skill. They are experts at sowing chaos and death among their foes, especially when their Infernal masters need an especially powerful foe dealt with.

Dread Strike

Beginning at 3rd level, you know how to sacrifice your own vitality to empower your strikes.

When you hit a creature with a weapon attack, you can choose to expend one of your Hit Dice to empower the attack with the following benefits:

• You can use your Sneak Attack on this attack, even if the attack does not meet the requirements for it.
• The damage for your Sneak Attack becomes Necrotic Damage.
• If the attack reduces the target to 0 hit points, you regain the Hit Die you expended to use this feature, and you gain temporary hit points equal to your Rogue level.

Forked Tongue

Also at 3rd level, you have been imbued with sinister power that fuels your abilities and alters your physical form.

You learn your choice of Abyssal or Infernal - depending on your choice, you gain additional benefits.

Abyssal

You gain proficiency in Intimidation. Whenever you make a Charisma (Intimidation) check, you can treat a d20 roll of 7 or lower as an 8.

Infernal

You gain proficiency in Persuasion. When you make a Charisma (Persuasion) check to convince a creature to agree to a bargain, contract, or agreement of any kind, you can treat a d20 roll of 7 or lower as an 8.

Sinister Vitality

At 9th level, you are able to draw life from the pain you inflict.

When you score a critical hit with a weapon attack, you can use your reaction to regain an expended Hit Die.

You can use this reaction a number of times equal to your Charisma modifier (minimum of once), and you regain any expended uses when you finish a long rest.

Hellish Curse

At 13th level, you are able to curse your foes with dark magic. 

When you hit a creature with your Dread Strike feature, you can mutter a curse in the language of your Forked Tongue, causing the target to be Blinded, Deafened, or be be unable to speak (your choice) until the start of your next turn.

Touch of Death

At 17th level, you become a master of the Infernal magic within you, and wield fury nearly equal to those of the Lords of Hell themselves.

When you use your Dread Strike feature, you can choose to expend any number of Hit Dice and force the target to make a Constitution saving throw (the DC of which equals 8 + your proficiency bonus + your Charisma modifier). On a failure, the target suffers one level of Exhaustion per number of Hit Dice you expend, up to 5 levels maximum.