Xanathar's Guide to Everything

Aganazzar's Scorcher

2-level Evocation

A line of roaring flame 30 feet long and 5 feet wide emanates from you in a direction you choose. Each creature in the line must make a Dexterity saving throw. A creature takes 3d8 fire damage on a failed save, or half as much damage on a successful one.
At higher levels: When you cast this spell using a spell slot of 3rd level or higher. the damage increases by 1d8 for each slot level above 2nd.