Wrath of the Stormlord

You call down the fury of the storm, surrounding yourself with a tempest of lightning and thunder. For the duration, each creature of your choice within 15 feet of you must make a Dexterity saving throw at the start of its turn. On a failed save, a creature takes 6d8 lightning damage and is pushed 10 feet away from you. On a successful save, the creature takes half damage and is not pushed.

In addition, as long as this spell is active, you are immune to lightning and thunder damage, and you have resistance to nonmagical bludgeoning, piercing, and slashing damage.

At Higher Levels: When you cast this spell using a spell slot of 8th level or higher, the lightning damage increases by 1d8 for each slot level above 7th.