Necrotic Tempest
Eldritch Storm
Storms infused with the essence of death roil with dark clouds that manifest leering skulls and bone-white lightning. Any creature exposed to the storm that isn’t a construct or an undead must succeed on a DC 13 Constitution saving throw at the end of each minute or take 3d6 necrotic damage.
A creature that dies in a necrotic tempest rises as a skeleton or zombie (your choice) 1d10 minutes later.
A necrotic tempest lasts for 1d4 hours and leaves crops withered and wells undrinkable for 1d4 days after its passing.
Source: Tasha’s Cauldron of Everything p. 163