You shoot out a beam of necrotic energy at a creature within range.  Make a ranged spell attack against the target.  On a hit, the target takes (2d4) necrotic damage, and must subtract 1d4 from the next death saving throw or ability check or saving throw that involves Constitution, as the beam saps a creature's vital force.  

This spell's damage increases by 2d4 when you reach 5th level (4d4), 11th level (6d4), and 17th level (8d4).