Crimson Lash

As part of casting this spell, you must expend a hit die or
the spell automatically fails. If you do, a writhing lash of
coagulated blood springs from your hand.
This magic weapon lasts until the spell ends. It counts
as a simple weapon with which you are proficient, and
it has the light, finesse, and reach properties. You can
choose to add your spellcasting modifier, instead of your
Strength or Dexterity modifier, to attack and damage
rolls with this weapon. Its damage die is equivalent to the hit die expended casting this spell, and the damage
dealt is necrotic. Each time a creature takes damage from
this magic weapon, its maximum hit points are reduced
by an amount equal to the damage it took.
At Higher Levels. When you cast this spell using a
spell slot of 3rd or 4th level, when you take the Attack
action, you can make two weapon attacks, provided both
are with this magic weapon. When you use a spell slot of
5th level or higher, when you take the Attack action you
make three weapon attacks, provided all are with this
magic weapon.