Death Warden

The sound of metal scraping against metal rings throughout the chamber as a powerful figure steps over the bodies of the dead. He sinks his massive, skull-adorned blade into the body of an orc, and a pale, ghostly smoke rises from the corpse, coils around the blade, and finally settles into a harsh symbol carved into its surface.

Blood flies as an elf moves relentlessly across the battlefield, slaying foes one after another with her twin blades, seemingly impervious to the attacks of her enemies. A massive beast rears up in front of her, a challenge even the mightiest of warriors would shrink before, but the elf only grins as she drives headlong into what must be certain doom.

Dripping water forms into icicles as they run down the shoulders of a heavily armored dwarf. The blizzard rages about him unnoticed. A silver-scaled dragon crashes into a nearby snowbank, its wings tattered by arrows and driving hail. It raises its head to stare the dwarf in the face, moments before his axe drives its way deep into its skull.

Whatever their original calling, all death wardens now serve the powers of death and destruction. Death wardens are ruthless and practical warriors, meting out death without mercy to any who stand in their way.

Death wardens are not born, but created. Skilled warriors transform themselves through profane rituals, becoming perfect killing machines. This process grants them powers over the dead. 

Undead Minion

Beginning when you choose this archetype at 3rd level, you gain the ability to create a loyal undead minion to serve you. You can raise a minion by spending 10 minutes performing a ritual over the corpse of any small or medium creature. Choose an undead type no larger than Large and that has a challenge rating of 1/2 or lower.

Add your proficiency bonus to your undead minion's AC and attack rolls, as well as to any saving throws and skills it is proficient in. Your undead minion gains proficiency in two skills of your choice, and also becomes proficient with all saving throws. For each level you gain after 3rd, your undead minion gains an additional hit die and increases its hit points accordingly. Like any creature, your undead mnion can spend Hit Dice during a short rest.

Your undead minion obeys your commands as best as it can. It takes its turn on your initiative, though it doesn’t take an action unless you command it to. On your turn, you can mentally command your undead minion to move (no action required by you). You can use your action to verbally command it to take the Dash, Disengage, or Help action. When you take the Attack action on your turn you can forgo one of your attacks to command your undead minion to take the Attack action. If you don't issue a command, your undead minion takes the Dodge action.

If you are incapacitated or absent, your undead minion acts on its own, focusing on protecting you and itself. Your undead minion never requires your command to use its reaction, such as when making an opportunity attack.

You can only have one undead minion at a time. If you try to create a second undead minion when you already have one, the old one turns back into a corpse.

Lichborne

Starting at 7th level, you gain resistance to necrotic damage, and gain advantage on saving throws to avoid being frightened or charmed.

In addition, your undead minion's attacks now count as magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage.

Wraith Walk

At 10th level, you can use your action to fade into a ghostly form, ending any grappled or restrained conditions affecting you. In addition, your speed becomes doubled, and your form becomes incorporeal allowing you to move through other creatures and objects as if they were difficult terrain. This effect lasts until the beginning of your next turn.

If you end your turn inside an object, you are immediately shunted to the nearest unoccupied space that you can occupy and take force damage equal to twice the number of feet you are moved.

Once you use this feature you can't use it again until you finish a short or long rest.

Master of Ghouls

Starting at 15th level, you can now have two undead minions at a time. If you try to create a third undead minion when you already have two, the oldest one turns back into a corpse.

Soul Reaper

At 18th level, you can use your action to reap the soul of a fallen humanoid creature to gain an additional use of your Action Surge class feature. The creature must be at 0 HP or dead for no more than one minute. Performing the reaping kills the creature instantly if it was not already dead. Once you have reaped a soul this way, you must finish a short or long rest before you can perform a reaping again.