Death Knight

Proficiency times per short rest you mas sacrifice an amount of HP to do extra damage with the next Melee attack that hits.   For each HP sacrificed you add an additional point of damage.  example. sacrifice 5hp and your next melee attack that hits will do an additional 5 damage.  The additional damage is the same as the base damage of the weapon being wielded.

Blood Soaked Bond

At 3rd level, you learn a ritual that creates a magical bond between yourself and one weapon. You perform the ritual over the course of 1 hour, which can be done during a short rest. The weapon must be within your reach throughout the ritual, at the conclusion of which you touch the weapon and forge the bond.

Once you have bonded a weapon to yourself, you can’t be disarmed of that weapon unless you are incapacitated. If it is on the same plane of existence, you can summon that weapon as a bonus action on your turn, causing it to teleport instantly to your hand.

This Bonded weapon is the only weapon that you can channel your death powers through.

Deadly Strike

At 3rd level you gain the ability to sacrifice HP to do additional damage.   Whenever you make a melee attack with your bonded weapon you may sacrifice a number of HP (max 25) and do additional damage on that strike based on the HP sacrificed.  You may use this ability a number of times per day equal to your proficiency bonus.

This ability scales at 10th level to do 1d4-1 damage per HP sacrificed and again at level 17 doing 1d4+1 damage per HP sacrificed.

Life Drain

At 7th level, you gain the ability to Heal yourself at the expense of your opponent.  As a bonus action you activate Life Drain and the next Melee attack with your bonded weapon does necrotic damage and heals you for as much damage as the attack does.

You may use this feature a number of times per long rest equal to your proficiency bonus.

Deathless

Gain advantage on death saving throws and gain max HP from Hit Dice used.

Knights Guard

Gain Proficiency bonus towards Armor Class as long as you are wearing Plate Armor

Deaths Embrace

Instead of healing one life per point of damage you do with Life Drain attack you instead heal 2 HP per point of damage you do.