You concentrate the raw magic flowing through your veins, and channel it into a blast of destructive energy.  The energy shoots out in a line 80 feet long and 10 feet wide.  Each creature in the line must make a Dexterity Saving Throw.  On a failed save, a creature takes (6d12) force damage, and has disadvantage on the next attack roll it makes before the end of its next turn.  On a successful save, a creature takes half as much damage, and suffers no other effect. 

At Higher Levels.  When you cast this spell using a spell slot of 5th level or higher, the spell's damage increases by 1d12 for each slot level above 4th.  The spell's area of effect length increases by 10 feet for each slot level above 4th.