Wave of Lethargy

Release a wave of sickening green energy in a 30-foot cone in front of you. Each creature in the cone must make a Constitution saving throw. On a successful save a creature suffers no ill effects.

On a failed save, a creature is Knocked Prone and immediately gains 2 levels of Exhaustion. Additionally, for the spell's duration, an affected creature cannot take Reactions, and can make only one attack each turn whenever it takes the Attack Action. 

An affected creature may repeat its saving throw at the end of each of its turns, ending the spell on itself on a successful save.

Exhaustion levels inflicted by this spell are removed when the spell ends for that creature.

At Higher Levels. When cast using a level 5+ spell slot, this spell inflicts one (1) additional level of Exhaustion for every two slot levels above 3.