Eldritch Affliction

You curse your target with a damaging affliction, racking their body with shadowy torment.

Make a ranged spell attack against the target. On a hit, the target takes 1d6 of either Force or Necrotic damage. At the start of your next turn, the target takes an additional 1d4 of either Force or Necrotic damage.

At the end of the second turn, you gain 1/2 of any Necrotic damage inflicted by the spell as temporary hit points.

This spell's damage increases when you reach 5th level (2d6 + 2d4), 11th level (3d6 + 3d4), and 17th level (4d6 + 4d4).

Note that any Warlock class feature that effects Eldritch Blast will also effect Affliction, which will fulfill any prerequisite requiring that spell.