Amnesia

A slim, curved blade made of adamantium is held by a grip wrapped in elegant, white dragon scales. With its sharp, dual-edged blade this weapon will slice, dice, stab and jab your enemies and shred whatever's left of them. The blade has a broad, curved cross-guard, creating the ideal weight balance to allow for smooth and accurate swings with this blade. The cross-guard has an elaborate dragon on it.

 

Whenever you kill an enemy with it's blade, make a DC 20 Charisma check, on a success, you regain health equal to half the enemies hit dice.

Hit points lost to this weapon's damage can be regained only through a short or long rest, rather than by regeneration, magic, or any other means.

Once per turn, when you hit a creature with an attack using this magic weapon, you can wound the target. At the start of each of the wounded creature's turns, it takes 1d4 necrotic damage for each time you've wounded it, and it can then make a DC 15 Constitution saving throw, ending the effect of all such wounds on itself on a success. Alternatively, the wounded creature, or a creature within 5 feet of it, can use an action to make a DC 15 Wisdom (Medicine) check, ending the effect of such wounds on it on a success.

In addition, this weapon counts as an arcane focus.

Once per long rest, you can use the sword's magic to tear a portal in reality to the Astral Plane. The portal is one way, and you can use a bonus action to close it.

Proficiency with a Longsword allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Damage: Necrotic, Eldritch Blast: Bonus Damage, Bonus: Hit Points per Level, Bonus: Magic, Warlock, Damage, Combat, Versatile, Sap