Ebon Water

You instill necrotic energy into up to 1,000 cubic feet (a cube 10 feet on a side) of water you can see. Each creature that enters the water or ends its turn in the water (not both in a single turn) takes 8d6 necrotic damage, or half damage with a successful Constitution saving throw.
A creature that drinks the water takes 8d6 necrotic damage and its maximum hit points are reduced by the same number, or it takes half damage and its maximum hit points aren’t reduced with a successful Constitution saving throw.
At the beginning of your turn, you can use a bonus action to move the necrotic energy up to 10 feet in any direction, as long as it remains in the body of water.