Thundaga

A vortex of lightning forming a cylinder 120 feet high and 15 feet wide is summoned from the snap of your fingers and cascaded upon your foes, leaving them paralyzed if they are fully within the area of effect. Larger enemies will not be paralyzed. This Black Magic Elemental spell is awarded to only the bravest of wizards and the cast spell has no friendly fire. Each enemy creature in the line must make a Dexterity saving throw. A creature takes 10d6 lightning damage on a failed save, or half as much damage on a successful one. The bolt ignites flammable objects in its path.

At Higher Levels: When you cast this spell using a spell slot of 5th level or higher, the damage increases by 1d8 for each slot level above 4th.