This elegant black-handled short sword resembles a wakizashi.  The blade pulses dimly with black light.

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 pull the targets blood from them via the wound left from the strike. At the start of each of the wounded creature's turns, it takes 1d4 necrotic damage for each time you've wounded it, and you receive the same number of hit points.  If you hit a creature with a roll of 19 or higher, the target must succeed a Constitution saving throw of 15 or be Stunned until the beginning of your next turn.

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

Notes: Damage: Necrotic, Stunned, warlock, Damage, Combat, Finesse, Light, Vex