Curse of Breathlessness

You attempt to lay a curse upon a creature within range, stealing the breath from its lungs, preventing it from holding its breath and forcing it to consciously focus on breathing, as it loses the ability to breathe automatically. The target creature must succeed on a Constitution saving throw or become cursed for the duration of the spell. While cursed in this manner, the target is unable to hold its breath and must expend its action or concentrate (as if concentrating on a spell) in order to breathe normally.

While cursed, if the target ends its turn without breathing, it takes 3d10 necrotic damage and suffers one level of exhaustion. Any levels of exhaustion caused by this spell go away when the spell ends. If the target is subjected to one or more conditions that prevent it from taking an action and concentrating (e.g. incapacitated), it has advantage on any saving throws it makes to break out of said condition(s), as it frantically struggles to draw breath.

A creature that does not need to breathe is unaffected by this spell.

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, you can target an additional creature within range for each slot level above 4th.