Unknowable Tears

An inky dark liquid flows from your eyes and spills into a dark purple undulating pool of ichor around you in a 15-foot radius, in which small tendrils can be seen writhing beneath the surface. The area within the pool is difficult terrain for creatures other than you, and it moves with you. When you cast this spell, choose a creature within 15 feet of you that you can see. Large tendrils rise from the pool to lash out at that creature, and it must make a Dexterity saving throw. On a failed save, the creature takes 4d8 necrotic damage, and half as much on a successful save.

On each of your turns until the spell ends, you can use your action to cause another tendril to attack in this way again, targeting the same creature or a different one.

Using a Higher-Level Spell Slot. The damage increases by 1d8 and the area increases by 5 feet for each spell slot level above 3.