Decompose

You cause the forces of entropy and decay to descend upon a creature. The creature you choose within range must succeed on a Constitution saving throw or take 6d6 necrotic damage and its movement is halved until the start of its next turn. On a successful save, the creature takes half damage and does not have its movement halved. 

Alternatively, you can cast this spell on a corpse within range.  A corpse immediately fails the saving throw and is aged 1d4 hours, as maggots and other creatures descend upon it. This aging counts against spells with time limits such as Revivify.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3rd. Additionally, the aging of corpses increases to 1d4 days (4th level), 1d4 weeks (5th level), and 1d4 years (6th level).