TFPH - Gurutho's Black Tithe

Take what is rightfully yours.

You invoke a powerful necromantic siphoning effect and become surrounded by a shroud of necrotic energy for 1 minute. The area around you becomes filled with shadows and a chill wind and is lightly obscured.

Each creature in the area that is not already slowed must make a Constitution saving throw against your spell save DC at the start of the spell, when they start their turn in the area, or when they enter the area for the first time on their turn. On a failure, a creature becomes slowed as by the Slow spell until the end of its next turn. On a success, the creature is not slowed.

A creature that is already slowed by this spell takes necrotic damage equal to your Constitution score when it starts its turn within the aura, or enters the aura for the first time on its turn. You regain hit points equal to the damage inflicted in this way.