You channel unholy strength into you hand, and reach out to grab a creature. The creature must make a Strength saving throw or become restrained by your deathly iron grasp. As an action on its turn, the creature can attempt to escape using a Strength (Athletics) or Dexterity (Acrobatics) check against your Spell Save DC.
At the start of the creatures turn while you maintain the grip and the spell, it takes 1d8 necrotic damage as you drain the life from it, and regain hit points equal to half the damage dealt.