Blood Rot

You force one creature within range to make a Constitution saving throw. On a failure, they take 1d8 necrotic damage at the start of each of their turns for the duration, and must subtract the damage dealt from any attack roll they make or hit points they gain until the start of their next turn. The targets Constitution score is reduced by a number equal to half the first amount of necrotic damage dealt. Their Constitution returns to normal after they finish a short or long rest. On a success, the target takes half damage and suffers no other effect. Undead, plants, and constructs cannot be affected by this spell.