Elemental Convergence

You channel the raw energy of the magic stones within your wand to release a devastating dual-elemental strike. A stroke of lightning forming a line 100 feet long and 10 feet wide blasts out from you in a direction you choose. Simultaneously, the bolt erupts into a fiery explosion at a point you choose within range.

Each creature in the line and each creature within a 20-foot-radius sphere centered on the explosion point must make a Dexterity saving throw. A creature takes 6d6 fire damage and 6d6 lightning damage on a failed save, or half as much damage on a successful one. 

If a creature is in the area of both the line and the sphere, it makes only one saving throw against the combined damage.