Headless Binding

Detach or Attach. Bonus Action to take the head off or put it back (hand, belt, sack, or shoulders). You can’t be killed by decapitation or by effects that need a head attached.

One Life, Two Parts. Head and body share Hit Points, conditions, and death saves. A detached head is a Tiny object (AC 13), not a creature. It can’t act. Area effects don’t hit you twice.

Far Sight. You always know the direction and rough distance to your head on the same plane. Within 60 feet, if the head isn’t bagged or Blinded, you see and hear through it and the body isn’t Blinded or Deafened. Farther than 60 feet, the body is Blinded and Deafened unless it has another sense.

Silent Body. The body can’t speak while the head is off. Verbal components still work if the head is within 60 feet and not silenced, gagged, or sealed.

Claim a New Head. If the current head is destroyed or on another plane, you are not instantly dead, but you are Blinded, and Deafened until you bind a replacement. Over 1 hour (can be part of a Short or Long Rest), bind the intact head of a Humanoid dead no longer than 3 days. Once per Long Rest.

Darkvision. 60 feet. If you hold your severed head aloft, the grin can shed dim light in a 10-foot radius. That light does not interfere with your Darkvision.

You have Advantage on Death Saving Throws.

Deathless Nature. Resistance to Necrotic damage. You don’t need to eat, drink, or breathe. You don’t require sleep, and magic can’t put you to sleep. You can finish a Long Rest in 4 hours spent motionless and aware

Death’s Charge. Uses equal to Proficiency Bonus, all back on a Long Rest. Spell save DC = 8 + PB + Wisdom or Charisma (pick the ability at character creation).
Know and Speak the Name (Bonus Action) of One creature you can see within 30 feet that can hear you. Wisdom save or Frightened until the end of your next turn. Undead make the save with Disadvantage; if they fail, they also take Necrotic damage equal to your PB.
Night Road (Bonus Action, only at night or in Dim Light/Darkness). Until the end of your turn, Speed +10 feet, and opportunity attacks against you have Disadvantage.

You can't willingly enter running water that is at least 1 foot deep. If you start your turn in such water, your speed is halved and you have Disadvantage on attack rolls and ability checks until you leave it. Still water, rain, snow, and crossing by bridge or boat do not trigger this trait.

Poisonous Gold: Gold is toxic to your binding. You have vulnerability to damage from weapons, ammunitions, and traps made of or coated with gold. If you touch gold with bare skin, you take 1d4 poison damage (no more than once per turn). While gold worth at least 1gp is in direct contact with your skin, you have the poisoned condition.

Brandish Gold: A creature you can see within 5 feet of you can use a Bonus Action to press or present a gold object worth at least 1gp. You must succeed on a Constitution saving throw (DC 8 + that creature's proficiency Bonus + its Strength or Dexterity Modifier) or take 1d4 Poison damage and have the poisoned condition until the end of your next turn. A given creature can use this benefit on you only once per Dusk.

Bound Horse, Unquiet Mount (1/long rest to summon if the horse is elsewhere. The bound horse is a warhorse with the following changes: undead (or construct) type, no need to eat or sleep, speed 60 feet, and it leaves no tracks. While you are mounted, difficult terrain from graves, mud, snow, or ruin does not slow you. If the bound horse drops to 0 hit points, it collapses to smoke and bone and returns at dusk the next day.

Guide or Cut
When a creature within 10 feet of you drops to 0 hit points, you choose:
Guide: it is stable. If it dies later before you finish a long rest, its soul is not easily bound; attempts to raise it as undead have disadvantage.
Cut: it dies. You can force it to skip death saves. Its soul is sent on; revivify still works, but animate dead and similar fail on that corpse for 24 hours.

Soul-Fire Eyes
While you hold the helm or wear it, you can see in darkness (including magical darkness) out to 60 feet, and you see the outline of souls in that range. Living creatures appear as a faint warmth. Undead, souls bound to flesh, and named targets burn colder and brighter. You cannot be blinded while the helm is on your shoulders.

Given Name (proficiency bonus / long rest)
As a bonus action, you speak one word: a name you have been given. That creature is Warranted for 1 minute. You have advantage on attack rolls against it, and it cannot willingly move farther from you unless it succeeds on a Wisdom save at the start of its turn. If you do not know a name, you cannot use this on a living creature.

Unfinished Judgment 
If you are reduced to 0 hit points and not destroyed by radiant damage from a destroy undead effect, the reaper can refuse you. Once per dawn, you instead drop to 1 hit point, the helm snaps back to your shoulders if it was separated, and each Warranted creature of your choice within 30 feet takes 1d10 necrotic damage. After you use this, you cannot speak at all until you finish a long rest—not even one word. The delay has a price. 

At Higher Levels. When you use this ability at higher player levels, the damage (both initial and later) increases by 1d10 at level 12, level 16, and level 20.

Pass Due
Once per turn when you hit a Warranted creature with a melee weapon, you deal extra necrotic or radiant damage (your choice) equal to your proficiency bonus + your level + 4 (round down). If the creature is undead, it cannot regain hit points until the start of your next turn.

Lantern of the Collar (1/long rest, 1 minute)
The soul-fire flares. In a 30-foot radius:
Undead have disadvantage on attack rolls and on saves against being turned or frightened.
Dying creatures automatically succeed on one death save at the start of their turn (your choice to allow this; default is yes).
You know whether each creature in the light is living, undead, or a soul out of place.
Allies can hear you clearly in this light even if you only speak one word.

The Name Spoken (1/long rest)
You speak a given name in full. One Warranted creature within 60 feet must make a Constitution save. On a failure, it takes 8d10 necrotic damage and is stunned until the end of your next turn as its stolen time is collected. On a success, half damage, no stun. If this reduces it to 0 hit points, it dies and cannot be raised as undead. A living creature killed this way can still be raised or resurrected by honest magic—Kelemvor allows a true return, not a mockery.