Cursed Blade of De'Urdvun II

Damage: damage dice + proficiency physical damage | damage dice + charisma mod necrotic damage or Draining Smite + charisma mod 

When Sated: damage dice + proficiency physical damage | 1 tier higher damage dice + charisma mod necrotic damage or Draining/Vengeful Smite + charisma mod

When Sated : Warlock spells deal your charisma mod in bonus necrotic damage, or add 1 to the save DC

Requires (your warlock level)*4 necrotic damage to sate modified by (your proficiency bonus) of (your damage dice), rolled when blade is present in combat for the first time each day

1 - subtracts 2 | 2 - subtracts 1 | 3 - adds 1 | 4 - adds 2 | 5 - adds 4 | 6 - adds 6

Track total necrotic damage done, notify DM when sated and at increments after (double, triple, etc)

Damage dice: 1d4 at 1st level, 1d6 at 6th level, 1d8 at 14th level, 1d10 at 20th, 1d12 for sated necrotic at 20th

All healing is halved until sated, with the other half counting towards sating

On a critical miss double the normal necrotic damage is done to the user (this counts towards sating the blade)

Draining Smite

Expend one spell slot to deal additional necrotic damage to the target of a melee weapon attack. The extra damage is 1d6 for a 1st-level spell slot, plus 1d6 for each spell level higher than 1st, to a maximum of 5d6. The damage dice increase to d8's against a target of good alignment. If the blade is sated, grant 1/4 the damage dealt as temporary hit points, rounded down, that last for 1 hour. Missing with a roll of (your proficiency bonus) or less deals half your normal necrotic damage to yourself

Vengeful Smite

While the blade is sated (once per short rest, max 1/2 your warlock level per day), you deal extra force damage to the target in addition to the weapon’s damage. The extra damage is based on your highest level spell slot (can include used slots), 2d8 for a 1st-level spell slot, plus 1d8 for each spell level higher than 1st, to a maximum of 6d8. The damage increases to d10's if the target has a good alignment. The user can instead choose to push the target back 2*(user's warlock level) feet with a strength saving throw based on your spellcasting dc, +5 if the target is good alignment. Missing with a roll of (your proficiency bonus) or less causes you to loose your sated state until your next source of necrotic damage.

This blade forms a direct link with the Demon De'Urdvun, whose endless thirst for the blood of mortals can only temporarily be sated.

This weapon serves as your spellcasting focus, and can be summoned using a bonus action (summoned for free as initiative is rolled unless surprised, dismissed as a free action).

The blade can take the form of any weapon you are proficient in the use of, and its form can be changed at the end of a long rest.

Every time the blade is present in combat, the link with De'Urdvun compels you to fulfill their lust for blood:

If the blade is not sated, half of all healing the user receives from any source is redirected into the blade until the blade would be sated. Sating the blade in this way does not grant the listed damage increase, or access to vengeful smite, but the next necrotic damage used in combat will fully sate the blade. On a long rest, any damage remaining before the blade would have been sated is dealt to the user, stopping at 1hp remaining. Any further remaining amount cannot be restored by any means until the following long rest (lowers hp max by that amount).

The blade remains sated until the user takes a long rest.

Necrotic damage dealt to a creature of good alignment counts double towards sating the blade, and dealing the final blow to a creature of good alignment drains their body of blood and deals 1/4 their maximum HP in necrotic damage, inducing 2 levels of exhaustion in the target. If the blade is sated, you are granted temporary HP equal to half that damage.