Abi-Dalzim's Horrid Wilting

You draw the moisture from every creature in a
30 ft cube. Each creature in that area makes a
Con save. Constructs and undead aren't affected,
and plants and water elementals make this save
with disadvantage. A creature takes 12d8 necrotic
damage on a failure, or half as much on a success.
Nonmagical plants that aren't creatures, such as
trees and shrubs, wither and die instantly.