Blight is a level 4 necromancy spell. This spell allows spellcasters to drain the moisture and vitality from a target creature using necromantic energy. It's especially effective versus plants.
Description
Deals 8d8Necrotic to a target. Plants take maximum damage from this spell, and have Disadvantage on the Saving throw against it.
The description given is not entirely correct in how the spell functions:
When the target of this spell succeeds in their saving throw, they still take half damage, regardless if they are considered plants or not
There are very few plants in the game. By the time you get this spell you're likely in Act II where all the plants are resistant to necrotic damage anyway, so the maximum damage clause is rarely relevant.
The incantation for Blight is Perē, the Latin command "vanish/be destroyed!"
Necrotic damage for each Spell Slot Level above 4th.
Disadvantage on the 
Saving throw against it.
No effect on undead and constructs.
Action + 
Level 4 Spell Slot
8d8 (8~64) 
Range: 9 m / 30 ft
Recharge: 