Fountain of Venom

9th-level transmutation
Casting time: 1 action
Range: 1 mile Target: Each creature within a 15-foot radius, 100-feet high cylinder within range
Components: V, S, M (an eyeball of a creature that died from a disease)
Duration: Permanent
Classes: Cleric, Warlock
Subclasses:

You cause a geyser of noxious poison to erupt in a 15-foot-radius that is 100 feet high, centered on a point on the ground you can see within range. The geyser erupts continuously, spewing its noxious poison until the effect ends. Creatures in the affected area are poisoned, and when a creature in the affected area attempts a saving throw or ability check, it takes 10d6 poison damage on a failure, or half as much on a success.

Additionally, any bodies of water in contact with the geyser become contaminated and unfit for drinking.

This spell immediately ends in its current space if you cast it again.