Dusk Wave

A beam of darkness forming a line 100 feet long and 5 feet wide blasts out from you in a direction you choose. Each creature in the line must make a Constitution saving throw. On a failed save, a creature takes 4d8 necrotic damage and is pushed 30 feet away from you and knocked prone. On a successful save, a creature takes half as much damage and isn't pushed or knocked prone. 
The darkness dispels any light created by a spell of 3rd level or lower.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d8 for each slot level above 3rd.